沥青软化点试验用到以下哪几种介质（）
A.自来水
B.蒸馏水
C.甘油
D.煤油
参考答案：B, C
请写出方程2x+y=5的所有正整数解（ ）。
“If,” he added at the meeting, “________ enough time, we would certainly have done it better.”
A．given
B．to be given
C．give
D．giving
