His father disappeared, ________ two children and never _______ from again.

A．left; being heard

B．leaving; heard

C．left; be heard

D．leaving; to be heard

货币政策下，在LM曲线形状基本不变时，IS曲线越平坦，LM曲线移动对国民收入变动的影响就越大；反之，IS曲线越陡峭，LM曲线移动对国民收入变动的影响就越小。