Agreement Of Tenses Clauses
1. I will send you the keys, if I can find them.
2. I should sing, if you asked me.
3. I should have gone to the seashore with you, if I could have arranged to leave my business.
4. If I had the money, I would lend it to you.
5. If I had owned the boat, I would have lent it to you gladly.
It is apparent that the tenses of the verbs in these clauses are governed by the tenses of the verbs in the principal statements.
The verb in a clause should take the form required by the tense of the verb in the principal statement