帮分析一道选择题 thanksmany people find it hard to make a living wit

我觉得这里over用做介词相当于during,如下
over = during:
Will you be home over the summer vacation?
Over a period of ten years he stole a million pounds from the company.
Can we talk about this over dinner?
还有since和during、over的区别如下：
During and over are used when you state the period of time in which something happens or changes
用于陈述事情发生变化的一段时期
• During her first year at college,she had several boyfriends.
• Over the last six months,crime has doubled.
Use since to say that something started at a point in time in the past,and is still continuing
用于陈述事件开始的一个时间点,而且事件还在继续发生
• He has been living in Leeds since 1998.
• We've known about it since May.
至于其它两个选项
across 从…一边到另一边,越过,标示位置,方位,不能表示时间
around 表示大约,环绕,也不符合题意
本题主要考察的是over做介词的用法：）