Our town________poor in the past,but great changes________in the town in the past three years. [ ]

A. was; had taken place  

B. was; have taken place

C. has been; had taken place  

D. has been; have taken place

在公路、铁路选线遇到滑坡时，下列（）种说法是错误的。

A．对于性质复杂的大型滑坡，路线应尽量绕避

B．对于性质简单的中小型滑坡，路线一般不需绕避

C．路线必须通过滑坡时，宜在滑坡体的中部通过

D．路线通过滑坡体的上缘时，宜采用路堑形式；路线通过滑坡体下缘时．宜采用路堤形式