物质的量相同的甲烷（CH4）和氨气（NH3），一定相同的量是（ ）
A．质量
B．体积
C．质子数
D．原子数
答案：C
— Where did Jim go yesterday?
— He ______ Guanzhou, but now he ______ back home. [ ]
A. goes to, has gone
B. went to, has been
C. has gone to, went
统计过程控制的特性是什么？
