—Guess, how much does it cost
—I think it costs ______ 15 and 20 dollars.

单项选择题计算机只懂机器语言，而现在人们一般用高级语言编写程序，将高级语言变为机器语言程序需经过( )。

单项选择题—Why are you standing there, Maggie —I can't see the blackboard clearly. Two tall boys are sitting ______ me.

单项选择题—Excuse me, when does Flight CZ3391 take off —One moment, please. I'll ______ it.

单项选择题She ______ as an animal trainer since 2003.

单项选择题Paper-marking is ______ of ancient China.