20世纪初，（）进行了动作研究和工作疲劳研究。
A.泰勒
B.吉尔布雷斯
C.马斯洛
D.赫兹伯格
参考答案：B
—Shall I go and buy some food for dinner?
—No, I have stored a lot in the fridge. That ______ be enough. [ ]
A. can
B. may
C. might
D. ought to
表达式operator + (x，y)还可以表示为【 】。
