以下是我做过练习中没弄明白的错题,我给出了正确答案和我自己选的答案,麻烦大家帮我指出我错在哪?为什么错?

以下是我做过练习中没弄明白的错题,我给出了正确答案和我自己选的答案,麻烦大家帮我指出我错在哪?为什么错?
分数50分,给出解析,一共11题,解析最全的回答做为最佳答案,毕竟是为了自己能弄懂这些题,要是解析能帮到我的话,
1.He will pass two milestones_____,that is,he will receive his master's degree and find a challenging job.
A.long ago B.not long ago C.before long D.long before
2.He's not got another job yet and it's not_____he will for some time.
A.likely B.easily C.nearly D.lonely
正确答案A,我选择B
3.A left-luggage office is a place where bags_____be left for a short time,especially at a railway station.
A.should B.can C.must D.will
正确答案B,我选择D
4.The managers discussed the plan that they would like to see_____the next year.
A.carried out B.carrying out C.carry out D.to carry out
正确答案A,四个选项分别解析一下
5.--What do you think made Mary so upset?
--_____her new bike.
A.As she lost B.Lost C.Losing D.Because of losing
正确答案C,我选择D
6.The lady said she would buy a gift for her daughter with the_____.
A.20 dollars remained B.20 dollars to remain
C.remained 20 dollars D.remaining 20 dollars
正确答案D,我选择B
7.There are five pairs_____,but I'm at a loss which to choose.
A.to be chosen B.to choose from C.to choose D.for choosing
正确答案B,我选择A
8._____in 1636,Harvard is one of the most famous universities in the United States.
A.Being founded B.It was founded C.Founded D.Founding
正确答案C,我选择B
9.The picture_____on the wall is painted by my nephew.
A.having hung B.hanging C.hangs D.being hung
正确答案B,我选择D,难道这不是用被动语态（画被挂在墙上）吗?
10.Sandy could do nothing but_____to his teacher that he was wrong.
A.admit B.admitted C.admitting D.to admit
正确答案A,我选择B,
11.I would have come earlier,but I_____that you were waiting for me.
A.didn't know B.hadn't know C.would have known D.haven't known
正确答案A,我选择B
提问截止至3月3号!

第一题,意思是：他将会在不久后通了两项大的测试（搬走了两块巨石亦可）,也就是说,他将获得硕士学位和一个具有挑战性的工作.A long ago 与B not long ago 都是讲很久以前和不久以前,时间都是发生在过去,与句意不符,D也是如此,before与long 两者位置不同,含义也不同,long 在before 前表示不久前,表过去；long 在before 后表示不久后,所以综上所述,此题根据词组所表示的时态就可以判断选择答案C.
第二题,意思是他还没有找到另一份工作,就目前而言他不可能找到工作,他还需要一些时间.此题根据句意可以直接排除CD选项.而A与B 则可根据句子成分而判定,此句后半句可写为：it's not likely for him that he will get the job for some time .之所以不用easily 是因为it在这里引导强调句型,句型为it is(not)加 形容词 加that 加 从句,而easily为副词,固不可用.
第三题,直接根据句意就可以选择,因为寄存行李是出于主观意识,而不是必须,如果用will或是A或D则表示每一件行李都将被寄存,不符合现在行李寄存的规则,所以选B
第四题首先排除B和D,因为see后不跟动词不定式,see carrying out 只表示看到部分执行的过程,与句意不符.此句是see (the plan )被执行,所以应该用被动,故排除C,选择A
第五题现在分词作主语回答what 的提问,第二句应该是：Losing her new bike made her so upset .
第六题动词ing作定语,修饰tweenty dollars.意思是“剩下的20美元”
第七题此题的意思是从五对中选一对,而不是选这五对,所以根据后句句意则选B
第八题此题为过去分词作状语,哈佛大学在1636年被建立,固选C
第九题hang 有悬挂的意思,表示某物悬挂在某处,picture和hang 是主动关系,所以用ing作定语.
第十题but意思为“除了”的时候,前面出现实意动词do的任意形式时,but后省略不定式符号to ,例如：I did nothing but wait.I have no choice but to wait .相比较这两句就明白了.
第十一题前半句是情态动词加have done 表示对过去的虚拟,而but 后指的是事实,所以要用一般过去时.