The explanation about general modal auxiliary verbs which refer to the present or future time (except could and would) can be read in MODAL VERBS. This part will only explain about the general modal auxiliary verbs with perfect infinitives which talk about the past activity ( except for will or shall ).
- WILL / SHALL + HAVE + PAST PARTICIPLE
See the use of this construction in the chapter explaining about “ Present Future Perfect Tense “.
- WOULD + HAVE + PAST PARTICIPLE
See the use of this construction in the chapter about “Past Future Perfect Tense“ and the chapter explaining about “ If-Conditional Sentence“.
- SHOULD / OUGHT TO + HAVE + PAST PARTICIPLE
e.g. – These plants can’t grow up well. You should have planted them in a right distance as the book says!
– The machine should have been tested first. Unfortunately, the operator believed too much to what the salesman said. Now, we cannot use it.
- MAY / MIGHT (possibility) + HAVE + PAST PARTICIPLE
e.g. – They may have entered through the back door. It is reasonable because it was the only door that wasn’t locked at that time.
– The audience may have given the appreciation to their performance if they had managed it professionally. They are talented dancers.
- MAY ( permission) + HAVE + PAST PARTICIPLE
e.g. – Many migrants may have planted some trees on the land around their house to improve their family’s income. But they were too lazy to do it. They left the land infertile.
– If the staff had known the deceit, they may not have stayed in that office any longer.
- CAN / COULD (ability) + HAVE + PAST PARTICIPLE
e.g. – Everybody could have expressed their opinion if they had been given the chance to. They were disappointed to the committee.
– Our students seemed to be very passive in that discussion though I believe that they could have argued well .
- CAN / COULD (possibility) + HAVE + PAST PARTICIPLE (for affirmative and interrogative only )
e.g. – He didn’t get his credit. Could the bank have made a mistake?
– Both of them had an intimate conversation in that party. They can have known each other before.
- CAN’T / COULDN’T (negative deduction) + HAVE + PAST PARTICIPLE
e.g. – He couldn’t have taken the chance in that competition because of his low ability.
– Their teachers can’t have encouraged them to do some positive activities supporting their learning process as students and teenagers. They lost for every competition.
- MUST ( positive deduction ) + HAVE + PAST PARTICIPLE
e.g. – The scientists must have spent their lives for this amazing discovery for years. It will be useful for the medical treatment.
– The police must have investigated it more than once. Their evidence is really accurate and liable.