两题英语选择题以及一些英语的语法问题.
1.I can think of many cases___students obviously knew a lot of English words and expressions but couldn't write a good essay.
A.why B.which C.as D.where
2.You can only be sure of____you have at present;you cannot be sure of something____you might get in the future.
A.that;what B.what;不填 C.which;that D.不填；that
什么时候该用both of+关系代词 ,什么时候该用both of+代词?
例如,last week,only two people came to look at the car,____wanted to buy it.
横线上应该填写both of whom 还是both of them?