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Should have and could have done, for what did not happen but ought to have.
Why you specifically
Cấu trúc modal of regret and criticism dùng để nói về một việc trong quá khứ lẽ ra nên làm nhưng đã không làm, hoặc một việc đáng lẽ có thể xảy ra nhưng không xảy ra. Dạng phổ biến nhất là should have + past participle, ví dụ You should have studied harder. Câu này thường mang sắc thái trách móc, phê bình nhẹ, hoặc hối tiếc sau khi mọi việc đã xảy ra. Could have + past participle thì khác: nó nói về một khả năng trong quá khứ, tức là việc đó đã có thể xảy ra nhưng thực tế không xảy ra, ví dụ We could have won the match. Sau should have và could have, tiếng Anh phải dùng past participle chứ không dùng động từ nguyên mẫu. Ví dụ đúng là should have told, could have gone, should have been, chứ không phải should tell hay could go.
The rule
Modals of regret and criticism are used to talk about a past action that did not happen, or happened badly, and to say what was the right thing to do. The most common form is should have + past participle, for example You should have studied harder. It often sounds like criticism, advice after the event, or regret about a past choice. Could have + past participle is different: it means something was possible or available in the past, but it did not happen, for example We could have won the match. Do not use the base verb after should have or could have. After these forms, English needs the past participle: gone, done, seen, told, left, studied.
The trap
You should call me yesterday.
You should have called me yesterday.
should have + past participle is used to criticise a past action that did not happen or was done badly.
We could finish the report last night, but we left early.
We could have finished the report last night, but we left early.
could have + past participle shows a past possibility that was possible but did not happen.
She should have take an umbrella because it rained heavily.
She should have taken an umbrella because it rained heavily.
After should have, English uses a past participle, not the base form of the verb.
I could help you, but you never asked.
I could have helped you, but you never asked.
Could have + past participle is needed for a missed past ability or opportunity.
Prove it
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