元世祖时,来华的外国人中最著名的是[ ]
A.马可·波罗
B.利玛窦
C.崔致远
D.高尔基
答案:A
She would lend me the money if I promised to ________ within a month.
A.bring it back
B.pay for it
C.pay it back
D.pay it out
氧气为什么要经过水封排入大气?