Three and four___seven.Two-thirds of the class_____.

问题描述:

Three and four___seven.Two-thirds of the class_____.
A.is;have worked it outB.is;have worked them out

选择A 第二个空是比较点,这里是说班上三分之二都能回答这个问题,也就是三加四等于7的问题,故用单数