1.Research___all over the world into the possible cause of c

1.Research___all over the world into the possible cause of cancer in the past years.
A.was made B.had been made C.has been making D.has been made
2.Fibers of hair and wool are not continuous and must normally be spun into thread___woven into textile fabrics.
A.as are they B.when to be C.that they are D.if they are to be
3.All the tasks____ahead of time,they decided to go on holiday for a week.
A.had been fulfilled B.having been fulfilled C.were fulfilled D.been fulfilled
4.He was ashamed ___to pass the exam.
A.to fail B.to have failed C.to be failed D.to be failing
用括号里给出单词的正确形式填空
_____(see) from the top of the tower,the professor gave us a warm welcome.
_____(finish) the painting,he began to make a frame for it.
_____(face) with difficulties,we must try to over come them.
2题答案是D,
还有填空_Seen____(see) from ..._Faced___(face) with difficulties.....我也很费解。
为什么___Having finished__(finish) the painting.用Having，而__Faced___(face) with difficulties用过去分词，

1、D 句中有in the past years 就要用完成时时态,research研究是被人研究,所以要用被动语态,并且在过去几年里,实则是从过去一直到现在的,影响到现在,所以要用现在完成时,因此选择D.
2、D 句子的意思是纤维和羊毛是不连续的并且如果他们要被编织成纺织物正常就必须被纺织成线.A选项as是正如、由于的意思,不符合,C选项that在这个句子中没有引导宾语从句和定语从句,排除,B选项when当.的时候的意思,可能放到句子里也还可以,但是缺少主语谓语,排除,并且用假设语气更加,如果.因此选D.
3、B 在这个句子中是用逗号连接的,这种情况下必须只有一个谓语动词,前者只能做伴随状语,因此用动词ing形式,任务是被完成,用被动语态,根据句意要用完成时.所有的任务都已经被提前完成了,他们才能.
4、B be ashamed to do是固定搭配,was是过去时,是过去的过去,要用过去完成时have failed.
填空：
第一空填seen ,逗号的前后两句根据句意可以发现是不同的两个主语,从塔顶看见了我们,教授热烈的欢迎我们,我们是被教授看见,这两个半句是不同的主语,而在这种情况下如前面所说只有一个谓语动词,因此要用过去分词表示被动语态的seen.
第二空填Having finished,began是过去时,说明完成绘画是这个动作之前的动作,要用完成时态,并且这句话是同一个主语he,因此用动词ing表示主动语态.
第三空填Faced ,其实这里有个短语be faced with是固定搭配,并且这句话的主语都是we,因此直接用Faced.
当遇到这种句型的时候,要看前后句的主语是否一致来判断是主动还 是被动,再看时态是什么来判断是否是完成时还是一般式.