为避免误解，应尽量不在“12点”位置以前（）_范围内注尺寸。
A.30°
B.45°
C.60°
D.90°
参考答案：A
-I have a toothache.
-You should __________.[ ]
A. drink lots of water
B. take a rest
C. see a dentist
D. have a good sleep
圆筒全屈服压力或极限压力
