当班内,对同单位、品种、发站的国内来煤进行取样时,以()作为一个检验批。
A、250;
B、500
C、1000
D、1500
参考答案:C
The computer doesn’t work well and it requires _____ but the manager requires me _____ to use it.
A.to change; to continue
B.changing; continuing
C.changing; to continue
D.to change; continuing
室温时将PH=5的硫酸溶液稀释1000倍后,则c(H+):c(SO42-)是( )
A.2:1
B.21:1
C.20:1
D.22:1