Adjective clause pronouns used as the object of a preposition

Example	Explanation
She is the woman. I told you about her.             a.       She is the woman about whom I told you.             b.      She is the woman whom I told you about.             c.       She is the woman that I told you about.             d.      She is the woman I told you about.	Formal English: the preposition comes at the beginning of the adjective clause.
The film was enjoyable. I and my friends watched it last week.           a.       The film to which I and my friends watched last week was enjoyable.              b.      The film which I and my friends watched to last week was enjoy.              c.       The film that I and my friends watched to last week was enjoy.             d.      The film I and my friends watched last week was enjoyable.	If preposition comes at the beginning of the adjective clause, only whom or which may be used.