题干
-- When will we go skating?
-- It depends when I will have free time.
A：in
B：to
C：at
D：on
答案(点此获取答案解析）
D
-- When will we go skating?
-- It depends when I will have free time.
A：in
B：to
C：at
D：on
Cu+Cu2+(未配平)。
气体产生；③溶液呈蓝色。