We want to know ______ better.[ ]
A. what to swim
B. how to swim
C. swimming
D. to swim
答案:B
某无色溶液中能大量共存的一组离子是( )
A.NH4+、H+、I-、CrO42-
B.Pb2+、Na+、Cl-、SO42-
C.Na+、Mg2+、Cl-、SO42-
D.Na+、Al3+、Br-、CO32-
运算电路如图所示,要使应取()kΩ。
A.8
B.12
C.18
D.15