齿轮油的型号用（）表示。
A.HL
B.HY
C.HS
D.HJ
参考答案：A
应紧急进行手术的肾损伤是（）
A.明显血尿
B.严重休克不能纠正
C.尿外渗
D.合并肋骨骨折
E.高热
More and more US students begin to learn Chinese at school ______ it is very difficult. [ ]
A. so
B. before
C. until
D. though
