Agriculture is the country's chief source of wealth, _________

单选题 I'm sure your suggestion will __________ the problem.

A．contribute to solving
B．be contributed to solve
C．contribute to solve
D．be contributed to solving

单选题 The house was very quiet, __________ as it was on the side of a mountain.

A．isolated
B．isolating
C．being isolated
D．having been isolated

单选题 My wife said in her letter that she would appreciate __________ from you sometime.

A．to have heard
B．to hear
C．having heard
D．hearing