A：2mol
B：3mol
C：4mol
D：5mol
用括号内所给单词的适当形式填空（1）What a____ (please) it is for me to play the piano with you!（2）Mother asked the Greens to help____(they) to some pears.（3）Tim sings even____ (badly) than before.（4）He felt____ (true) sorry for what he said.（5）____ (clean) work is to make our city clean.
若2x2y2b+3与 12 xa+1y 23b−1 是同类项，求a，b的值．
— Hi, Tom. Is your sister as active as you?— No, she's a quiet girl. She is ________.
