We all feel it is Jack as well as his wife that ________ for their son's bad performance at school.

A．are to blame

B．is to be blamed

C．are to be blamed

D．is to blame

国家基本比例尺1：25000、1：50000、1：100000地图编绘中，图廓边长与理论值之差不大于（）毫米。

A、±0.15

C、±0.25

B、±0.20

D、±0.30