请问几道LZM语法的题

关于

1.P69第7题:
The Rorschzch test is gaining new respect as a diagnostic tool because it takes only one hour to expose behavior and thought processes that may be unlikely to emerge in other procedures or weeks of ordinary interviewing.
(A) that may be unlikely to emerge in other procedures or weeks of ordinary interviewing
(B)whose emergence is unlikely in other procedures or weeks of ordinary interviews
(C)that might not emerge in other procedures or in weeks of ordinary interviews
(D)that may not emerge under other procedures or weeks of ordinary interviews
(E)unlikely not to emerge during weeks of ordinary interviewing or in other procedures
答案是C,但是根据GMAT语法规则,may与might在语法中只有时态的区别,而没有其他区别,这里用过去式might是不是有点不合适呢?另外,答案说A,B,D中or后的介词不能省略,为什么啊?

首先我想答案a,LZM还是解释得很清楚的, may 和 unlikely在这里语义重复了。至于might 和may区别还是有的，might虽然是may的过去时。但是我还查到美国传统字典上might的解释是：

1.Used to indicate a condition or state contrary to fact:
She might help if she knew the truth.
2.Used to indicate a possibility or probability that is weaker than  may:
We might discover a pot of gold at the end of the rainbow.
3.Used to express possibility or probability or permission in the past:
She told him yesterday he might not go on the trip.
4.Used to express a higher degree of deference or politeness than  may, ought, or  should:
Might I express my opinion?

当然我认为在这道题目中might就是may的过去时，不过这里用过去时是恰当的。作者如何能肯定今后都不会有测试方法能超过Rorschzch test ，他只能是对过去的可能性的一种判断。他只能是认为“前无古人”，不敢说“后无来者”的