我国人口分布的基本特点是(    )

设a＞b，则下列各式中不能成立的是（   ）

⊙O₁、⊙O₂、⊙O₃两两外切，且半径分别为2cm，3cm，10cm，则△O₁O₂O₃的形状是(     )

A：Hi，Bill！____.

B：Yes.I've already finished my homework.

A：____.

B：I'd like to work outside.

A：Me，too！____.

B：I'd like to do something to help others.Would you like to go with me?

A：Sure！Let's come up with a plan.____.In the afternoon we can visit the children's hospital to cheer up the sick children.What do you think?

B：____. But we had better join the school weekend volunteer program.

A：Good idea！We could do better then.