III. DESCRIPTIVE/INTERPRETIVE FUNCTION OF MODALS: DESCRIPTIONS FROM THE SPEAKER'S POINT OF VIEW (OPINION)
3. Introduction to Modals of Probability (Predictions or Certainty)
3.4 Using Modals of Probability in the Present, Past and Future
3.4.2 Probability in the Past: Must Have/Must Not Have
We can use modals to make a prediction about the cause of something in the present. There are different levels of certainty for predictions about the past:
3.4.2.1 Strong Certainty
When we are quite sure of a possible cause.
- Use 'must have' + past participle for actions as the probable cause.
- Use 'must/would have been' + modifier to describe something in a Subject + Linking Verb + Modifier Sentence.
- Use 'must/would not have' or 'couldn't have' as the negative form.
Example
That loud sound must have been thunder. It was raining last night.
For speaking only, use 'mustn't have' as the negative form.
Examples
Everything is wet. It must have rained this morning. (use 'must have' + past participle)
The cake is gone. Someone must have eaten it.
My car is not running well again. The mechanic couldn't have fixed it properly.
Carlos did not come to the meeting. He is always very responsible. He must not have gotten the message.
When using a cause in the form of a modifier (noun, adjective, participle, adverb):
- Use 'must have been' or 'couldn't have been' + modifier.
Examples
It made a rattling sound when we got close to it. It must have been a rattlesnake.
They left a message on our door. They must have been here this afternoon.
3.4.2.2 Weaker Certainty: Could Have, May Have, May Not Have, Might Have, Might Not Have
- Use 'may have', 'might have', 'could have' + past participle for actions with weaker certainty about the cause.
- Use 'may not have', 'might not have' as the negative form.
- Use 'may/might + have been' + modifier to describe something in a Subject + Linking Verb + Modifier Sentence.
Examples
Maria didn't eat much at dinner. She may have been sick.
My friend didn't return my text message. He might not have checked his messages yet.
I fell quite badly while I was hiking. I might have broken my leg.
They aren't here yet. They could have gotten in a traffic jam.
He didn't work very hard on the project. He must not have been excited about it.
It barked when we saw it. It must not have been a bear.
When there is weaker certainty about a cause in the form of a modifier (noun, adjective, participle, adverb):
- Use 'must have been' + modifier
Example
He must have been scared when he saw that movie. It is a terrifying movie.
Exercise 1: The following paragraph uses modals of probability in the past.
First, write the modals that express probability in the past. Then, indicate whether the modal that is used has weak (write 'w'), medium (write 'm'), or strong (write 's') probability.
A Bright Light
A: Did you see that bright light in the sky yesterday?
B: What bright light?
A: Well, it just lit up the whole sky, and it was just hanging there—not moving at all.
B: OK? Well, it must have been the moon then.
A: No, it couldn't have been. The moon was also in the sky—in another place.
B: What? Okay, then it could have just been a very bright star.
A: No, it couldn't have been. It was much brighter and bigger than a star.
B: OK. So, do you think it may have been a meteor?
A: No, it couldn't have been a meteor. It wasn't moving.
B: Well, you may not have seen a meteor, but are you sure that your mind is not playing tricks on you? Could you have stayed out a little late last night? Maybe you could have drunk a little too much last night, huh?
A: No, I was wide awake. I took a nap in the afternoon, so I couldn't have lacked sleep—and I didn't drink anything.
B: Well then, what do you think you could have seen?
A: I'm not sure, but it had windows in it, and I could see little green men inside of it.
B: Well then, I think that you must have been feeling a bit crazy then. Been to a doctor lately?
Exercise 2: Fill in the blanks with a modal form using the different probabilities for a certain level of probability (weak, medium, strong).
Use the context of the sentence to decide whether a weak, medium, or strong modal should be used for that situation.
Stronger modals of probability: 'must have', 'must not have', 'couldn't have', or 'would have'
Weaker modals of probability: 'may have', 'could have', 'may not have' or 'might not have'
1. When Elif didn't call after being out until 2:00 a.m., her mother (BE) so angry.
2. Some people think that the Great Chicago Fire of 1871 (start) because a cow in a barn kicked a lantern over into the hay, lighting the barn on fire.
3. I don't know why Yusuf didn't come to the meeting. (know) the right time. Did anyone tell him when the meeting started?
4. When a 'prank' Halloween radio broadcast of an alien Martian (Mars) invasion of Earth came over the radio, people (BE) absolutely terrified.
5. The accident (avoid). A black bear suddenly ran out of the trees beside the road at night, when it was very dark.
6. Filip (taken) my suitcase by mistake. It looked exactly the same as mine.
7. When teacher Christa McAuliffe took off on the U.S. space shuttle on January 28, 1986, she (know) about the explosion of the shuttle that was soon to happen.
8. When the first astronauts landed on the moon, they (BE) amazed when they saw the Earth from so far away.
9. Chiara (avoid) the embarrassment of making a mistake on her violin in front of 300 people if she had just practiced a little harder.
Exercise 3: Finish the sentence or write another sentence to make predictions about the following using the different probabilities that are indicated.
Stronger modals: 'must have', 'must not have', or 'couldn't have'
Weaker modals: 'may have', 'could have', 'may not have' or 'might not have'
1. When Jakob got here, he was all wet. (must have)
Trả lời:
2. Caroline was so angry when she left her supervisor's office. (must not have)
Trả lời:
3. Julia decided to drive to Mexico instead of flying. (couldn't have)
Trả lời:
4. Aurora was so angry. (may have)
Trả lời:
5. Yuka left her laptop at the restaurant. (could have)
Trả lời:
6. Lukas ran out of gas on the way here. (may not have)
Trả lời:
7. Krishna didn't get the money that she had asked her parents for. (might not have)
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8. Write your own sentences using the following modals:
a. (could not have, couldn't have)
b. (must not have been)
c. (may have)
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