题干
—I'm sorry I stepped outside for a smoke.I was very tired.
—There's no________for this while you are on duty.
A：reason
B：excuse
C：cause
D：explanation
答案(点此获取答案解析）
B
，据此推断该氧化物（ ）
CH3COO－＋H+ 对于该平衡，下列叙述正确的是
