Mr. Baker is very interested in our plan. I spoke to him on the phone last night.

A. Mr. Baker is very interested in our plan to whom I spoke to on the phone last night

B. Mr. Baker, who is very interested in our plan, I spoke to on the phone last night

C. Mr. Baker, to whom I spoke on the phone last night, is very interested in our plan

D. Mr. Baker, who I spoke to on the phone last night, is very interested in our plan