Распространенные ошибки
Use the present infinitive without to, not the past tense after the auxiliary did.
the answer to a question beginning with did is always in the past tense: Did you see the picture? -Yes, I saw the picture; or Yes, I did.
We also use the present continuous for the future when something is pre-arranged or expected with some certainty: Lorna is arriving tomorrow at six. Tom and I are eating out tonight
The verb after a since clause of time is generally in the present perfect tense.
If we are speaking of the result of a past action rather than of the action we must use the present perfect tense. When somebody says, I have seen Panthenon, he or she is not thinking so much of the past act of seeing it, as the present result of that past action.
When the verb in the main clause is in the past tense, use a past tense in subordinate clauses.
This rule doesn't apply (1) to verbs within quotations, (2) to facts that are true at all times. We say:
1. She said, 'I am waiting for your answer'
2. He said that London is a great city