加速器等中心立体定向照射时靶位置的不确定度为（）
A.1mm
B.2mm
C.3mm
D.4mm
E.5mm
参考答案：A
图中A、B、C、D是立在水田中的电线杆的铁丝拉线的四个部位，其中最容易生锈的是( )
A.A处 B.B处 C.C处 D.D处
All the children on the playground stared up into the sky until the noise of the plane _____.[ ]
A. gave up
B. took off
C. went out
D. died away
