The family has been in American_.a.for a last year b.since last year为何选 aI _ for mushrooms but I haven't found any.a.have been looking b.have looked为何选 a,b 错在哪It was so dark outside that he_.a.didn't dare to go out to fetch waterb.dare not to fetch water为何选 a
The family has been in American_.
a.for a last year b.since last year
为何选 a
I _ for mushrooms but I haven't found any.
a.have been looking b.have looked
为何选 a,b 错在哪
It was so dark outside that he_.
a.didn't dare to go out to fetch water
b.dare not to fetch water
为何选 a
The family has been in America_.
a.for a last year b.since last year
为何选 a
==>绝对应该选b, 没有a这种说法。since在这里是介词，谓语用现在完成时没错,表示从去年起到现在还住在美国，这个句子是现在完成时的典范，我楼上的人竟然还可以编出一番歪理? 不知道谁告诉你选a的。
顺便说一下，American应该是America.
I _ for mushrooms but I haven't found any.
a.have been looking b.have looked
为何选 a,b 错在哪
==>选b的话从句的时态不对，应该用过去式。而A是现在完成进行时，表示过去在找，现在还在找。
这样说也是对的：I have looked for mushrooms but I didn't find any.但是意思就有变化了－－－现在已经没在找蘑菇了。
It was so dark outside that he_.
a.didn't dare to go out to fetch water
b.dare not to fetch water
为何选 a
==>dare后面有to的时候，显然dare不是情态动词而是实义动词，既然它不是实义动词就应该有时态的变化，而且实义动词也不能直接在后面加not表示否定:一定要借助助动词来否定，b去掉to就对了。
晕...
原则就是哪个长选哪个....哈哈,下面的只是个人的理解
第二个 的look for 是个和go 一样的不可以直接用于完成时的动词,所以a
第三个 的dare是vi.动词,否定就是靠didn't
从语法角度来讲这几个选项都没有错,只是语义不同,要根据上下文意思来理解.1.for a last year 意思是已经在美国一整年了,强调这一整年都在,last 表示一个持续的概念.since last year 意思是自从去年就在美国了,强调从...