From which field of science do we learn a lot about the planets

A. was deep in thought of his past
B. was thinking of who Lee was
C. was thinking of how to teach his class
D. was having a talk with another passenger

A. All TV sets can receive some programs without paying money in a certain area.
B. You may pay for some special programs if you like.
C. If you are interested in a certain subject, you may borrow some video tapes about it.
D. All of the above.