—When did your father stop smoking?
—In 1999, the year I was born.
A:put up
B:think up
C:mix up
D:give up
互联网给我们的学习带来了极大有方便.假如你在百度搜索引擎中输入“马关条约”、“通商口岸”、“双十协定”这三个关键词,最有可能出现的城市是( )
已知⊙O1与⊙O2外切于点A,⊙O1的半径R=2,⊙O2的半径r=1,若半径为4的⊙C与⊙O1、⊙O2都相切,则满足条件的⊙C有( )