在硫化氢(H2S)中,硫元素的化合价为( )
A.+4
B.+6
C.-2
D.-1
答案:C
There is _____ wrong with this computer. It doesn't work well. [ ]
A. something
B. anything
C. everything
D. nothing
贵重药材,为了更好地煎出有效成分,宜采取另煎的方法。