单项选择题
The troops have been on the（）for a possible enemy at tack.
A．alarm B．alert C．warning D．notice
单项选择题 Some philosophers insist that one way to（）knowledge is through an empirical approach.
单项选择题 Until the final votes are cast, though, assurances（）for nothing.
单项选择题 All students have free（）to the library.
