I think ... my friend. a)of B)with C)for

I think of my friend. — Я думаю о моем друге.

I don't think of my friend. (Negative).

Do I think of my friend? (General question).

Who thinks about his friend? (Special question).

What do I think? (Special question).

Do I or does she think of my friend? (Alternative question).

Do I think of my or his friend? (Alternative question).

Do I think of my friend or parents? (Alternative question).

I think of my friend, do not I? (Disjunctive question).

I thought of my friend. (Past Indefinite).