高一定语从句

Question

1.Is this factory_______some foreign friendsvisited last Friday?
A.that B.where C.which D.the one
2.Have you seen the boy__________?
A.that I told B.I told you of C.whom I told you D.I told you of him
3.Mr.Smith will never forget the days________he spent with his students.
A.when B.which C.during which D.on which
4.The team_________waiting for finally arrived.
A.we have been B.who we are C.whom we have been D.we had been
求每题的详细解释，本人定语从句搞不太懂，请高手帮帮小弟，感激不尽~.~

Answer 1

第1题：
答案是C。将句型还原：This factory is ______ some foreign friends visited last Friday.
主句部分缺少表语，即定语从句缺少先行词和关系词，从句子看，关系词代替先行词在定语从句中作visited的宾语，故可省略。the one 不定代词，代指 factory 之一。
第2题：
答案是C。tell是及物动词，可带双宾语，形式为：tell sb sth. 在题中，先行词the boy是 tell的直接宾语，you是tell 的间接宾语。故选C。(A缺间接宾语，B多用了介词of，D多用了介词of 和代词him.
第3题：
答案是B。定语从句中，spent是及物动词，需带宾语。spend sth (time) with sb. 与某人一起度过。
第4题：
答案是D。关系词代替先行词team作介词for的宾语，故可省略。主句的时态是过去时，而从句的时态发生在主句动词之前且一直在进行，故应用过去完成进行时。

Answer 2

第一题选D 在句中作表语并做先行词，因为在句中作宾语，所以省略关系代词that。要还原成陈述句：this factory is the one some....如果题目为is this the factory__,这时可选 A C。
其他一楼为正解。

Answer 3

A C C A