His success in his career was due to his determination __________ what seemed impossible.

A．of doing

B．with doing

C．doing

D．to do

(2013·陕西师大附中模拟)If we had taken such effective measures much earlier, the river ________ so seriously now.

A．is not polluted

B．would not be polluted

C．had not been polluted

D．would not have been polluted