modals??????

English as a Second Language English Vocabulary, Grammar and Idioms
1

Mary . . . her alarm clock last night because she overslept and was late for school.
1.can’t have set 2.should have set
I thought both answers were correct but the answer key says only 2 is correct
why can I not use 1 here?

2

I would say the first option is also possible, but only with a comma after the word ‘night’.

1. Mary can’t have set her alarm clock last night, because she overslept and was late for school (this morning).

[color=darkblue]_________________________________________________________________________
[size=75]“If people are good only because they fear punishment, and hope for reward, then we are a sorry lot indeed.” ~ Albert Einstein[/size]

3

[quote=“Biglittleboy”]
Mary . . . her alarm clock last night because she overslept and was late for school.

  1. can’t have set 2. should have set
    I thought both answers were correct but the answer key says only 2 is correct[color=blue].
    [color=blue]Why can I not use 1 here? [color=blue]Because we are talking about the past, so ‘couldn’t have set’ would be correct. Thus, the only correct choice is #2. Remember that ‘couldn’t’ is the past tense of ‘can’t’.
4

Hi Canadian,

Though I would agree that ‘couldn’t have set’ is a possible wording, it is definitely NOT incorrect to say ‘can’t have set’. The choice would be somewhat context dependent.

I view it this way:

  • She can’t have set her alarm clock = I refuse to believe that she set her alarm clock (or I find it impossible to believe that she set her alarm clock).

  • She couldn’t have set her alarm clock = It wasn’t possible that she set her alarm clock (OR it wasn’t possible for her to have set her alarm clock)

Here’s a link to a thread that has an example:
can’t have done
[color=white].

5

[quote=“Esl_Expert”]
Hi Canadian,

Though I would agree that ‘couldn’t have set’ is a possible wording, it is definitely NOT incorrect to say ‘can’t have set’. [color=blue] I just don’t agree with your view. I agree with the tester.

6

Thank you, ESL Expert, for those VERY helpful examples.

They seem to agree with the examples given by two scholars:

INFERENCE

  1. She can’t have finished the entire assignment yet. [As you might put it: I refuse to believe that …]

POSSIBILITY

  1. He could have come on the early train. [As you might put it: It was possible that …]

James

Source: Marianne Celce-Murcia and Diane Larsen-Freeman, THE GRAMMAR BOOK (1983).

(Now excuse me while I print out your examples for my collection.)