The magic show has been on 20 minutes. It has been on 2.p.m.
A:for, since
B:in, since
C:for, for
D:since, for
两个氨基酸分子脱水缩合形成二肽时生成一分子水,该水分子中的氢来自于( )
下列词语中划线字的读音完全正确的一项是