题干
It might have saved me some trouble ______ the schedule.
A：did I know
B：have I known
C： do I know
D：had I known
答案(点此获取答案解析）
D
It might have saved me some trouble ______ the schedule.
A：did I know
B：have I known
C： do I know
D：had I known
PCl3(g)＋Cl2(g) ②2HI(g)