题目

It just isn't fair that ____I was working as a waiter last month，my friends were lying on the beach．（ ） A．.while     B．whenever     C．though   D．for 答案：A5．有机物C5H12O4能与金属钠反应，只含有一种官能团，且官能团在不同的碳上，符合条件的有机物有（　　）种，（　　）A．3B．6C．8D．7