The price of the housing is rising rapidly and nowadays lots of money _______ on houses. [ ]

A. is spent

B. has spent

C. is cost

D. is paid

利用数学模型，以时间的延伸推断预测的方法是（）。

A.平均法

B.移动平均法

C.指数平滑法

D.趋势外推法