IMO: D

(D) for me.

When the prime lending rates went up in 1987, economists determined they would cause interest rates to rise and then decline over the ensuing five-year period.

　　(A) they would cause interest rates to rise and then decline they unclear, rates or economists

　　(B) they would mean that interest rates would rise and then decline they unclear, rates or economists

　　(C) that they will cause interest rates to rise and then decline they unclear, rates or economists

　　(D) that the increase would cause interest rates to rise and then decline correct, clear and concise

　　(E) that the increase would cause interest rates' rising and subsequent declining cause interests rates' rising is wordy