一般规定,如果DJ6型光学经纬仪两个半测回角值之差不超过()时,取其平均值作为一测回的角值。
A.±40″
B.40″
C.±13″
D.13″
参考答案:A
I _______ play the guitar. It's too difficult(难的).[ ]
A. can
B. can't
C. don't