题干
The boy looked to the right and to the left, ______ what to do
A：not to know
B：didn’t know
C：not knowing
D：not being know
答案(点此获取答案解析）
C
A：not to know
B：didn’t know
C：not knowing
D：not being know
H2O2＋NaCl 
H2O＋O2↑