—That must have been a long trip.

—Yeah, it _____ us a whole week to get there.

A．takes

B．has taken

C．took

D．was taking

当国民收入在乘数和加速数的作用下趋于下降时，其减少将受到下述哪项因素而放慢( )

A．失业增加

B．边际消费倾向下降

C．加速系数上升

D．总投资降为零