一般来讲，只有容易储藏和保存、不易变质的商品才适合做期货品种。( )
参考答案：对
–When did he come back last night?
--It was at 8 o’clock ________ I was watching a documentary on TV.
A．since
B．that
C．when
D．which
有一条指令用十六进制表示为 CD21，用二进制表示为______。
A．1.1011100001E+15
B．1.1001101001E+15
C．1.10011010001001E+15
D．1.10111000001001E+15
