A:①②③④
B:①②③
C:②③④
D:①④
氨是生产氮肥的原料,氨水也可直接做氮肥使用氨(NH3)中,氮元素的化合价为____ 。其氮、氢元素质量比=____ 。
⑴Can I help you? ____ A. Of course.
⑵Are they OK?____ B. Yes.
⑶Can I try them on?____ C. Thank you.
⑷Here you are!____ D. No. They're too small.