保险合同是一种()合同。
A.有偿
B.双务
C.单务
D.无偿
E.等价有偿
参考答案:A, B
— I'd like your help tomorrow.
— No problem, but can you be more _______ so that I can make advance preparations?[ ]
A. serious
B. brief
C. formal
D. specific
标注斜度、锥度时,符号方向应与斜度、锥度方向()。
A.一致
B.垂直
C.斜交
D.无关