单项选择题
（）from space，the earth，with water（）seventy percent of its percentage，looks like a “blue ball.”
A.Seen；coveredB.Seeing；coveringC.Seeing；coveredD.Seen；covering
单项选择题 Though the book is a little expensive，it is（）.
单项选择题 It is required that students（）mobile phones at school，so seldom（）them using one.
单项选择题 She is doing the work（）I like it（）.
