15.It’s useless ______ to persuade him to get rid of that habit;he just can’t make ______.
A.trying;it B.to try;that C.trying;that D.in trying;it
解析：It’s useless doing sth.“做某事没用”；make it“做到”。
答案：A
§3.3 介词、副词填空
14.She will join us ______ one condition:that we divide all the profits equally.
A.in B.for C.on D.to
解析：on one condition“有一个条件”。
答案：C
13.Since she is angry,we might as well ______ her alone.
A.leave B.to leave C.leaving D.left
解析：might as well do sth.“还是做……为好”。
12.His theory was so ______ that few people could understand it at that time.
plete plex C.curious tent
解析：他的理论太复杂，当时没人能看懂。
答案：B
11.I promise that you ______ have five dollars if you clean all the windows.
A.will B.would C.shall D.should
解析：shall用于第二或第三人称时，可表示许诺。
10.They spent three months at ______ sea before they went on ______ shore.
A.the;the B./；/ C.the;/ D./；the
解析：at sea“在海上航行”；go on shore“上岸”。
9.-Do you have any new dictionaries?
-We’ve got ______ at the moment.
A.no one B.not one C.none her
解析：我们现在一本新词典也没有。none代指no new dictionary。
8.After the trial,the judge passed judgement ______ her and she was sentenced ______ 3 years in prison.
A.to;to B.on;on C.on;to D.to;on
解析：pass judgement on“对……宣判”；sentence sb. to…“判某人……徒刑”。
7.I ordered that the gate ______ to keep the cows and sheep out.
A.was locked B.must be locked
C.be locked D.would be locked
解析：order后面接that从句时，从句中的谓语动词用虚拟语气。
6.The slave owner ordered the slaves to go down ______ when he walked by.
A.on their knees B.on their knee C.to their knees D.to their knee
解析：go down on one’s knees是固定短语。