南极洲冰层的平均厚度达2000多米，素有“ ____ ”之称．
She doesn't want to see anyone now. She just wants to be left a____.
如果命题p(n)对n＝k(k∈N＋)成立，则它对n＝k＋2也成立．若p(n)对n＝2也成立，则下列结论正确的是( )
What does Mark do?
读图完成下列要求．
