定语从句.求详解1. When you read the book, you'd better make a mark

定语从句.求详解
1. When you read the book, you'd better make a mark ____ you have any questions.
A.at which B.at where C.the place where D.where
（A为什么错了,介词应该用哪个,C呢）
2. I can still remember the sitting room ____ my mother and I used to sit in the evening.
( 为什么是不能用which,总觉得这类可以选which,)
3. All ____ is needed is a supply of oil.
A.the thing B.that C.what D.which
(AB两项的区别)
4. In the dark street, there wasn't a single person ____ she could turn for help.
A.that B.who C.from whom D.to whom
5. I shall never forget these years ____ I lived in the country with the farmers, _____ has a great effect on my life.
A.that, which B. when, which C. which. that D.when,who
6. It was an exciting moment for these football fans this year, _____ for the first time in years their team won the World Cup.
A.that B.while C.which D.when
（why not C）
7. All of the flowers now raised here have developed from those _____ in the forest.
A.once they grew B.they grew once C.that once grew D.once grew
( CD 不太清楚)

看来你对定语从句的基本概念还是比较模糊的.
第一,被定语从句所修饰的那个名词叫作“先行词”；第二,连接先行词和定语从句的连接词叫做关系代词或关系副词.第三,到底用哪个关系词是要根据先行词在定语从句中所担任的成分来决定的.
如：This is the factory ______ my father used to work.
This is the factory ______ I visited last week.
This is the factory ______ produces TV sets.
上面3个句子先行词都是factory,但是第一句中的factory在定语从句中作地点状语（my father used to work in the factory),所以要填where或in which；第二句中的factory在定语从句中作visit的宾语(visit the factory),所以要填that/which或者不填；第三句中的factory在定语从句中作主语(the factory produces TV sets),因此要填that/which,但不可以省略.
1.不是定语从句,是考查地点状语从句的,因为mark不可能在定语从句中担任成分,不可能说you have any questions at the mark,所以也不能用at which.只能理解为“在有问题的地方做记号”,即you have any questions只能表示地点,用where表示.如果选C,要说成at the place where,但显然太罗嗦.
2.先行词the sitting room,在定语从句中作地点状语,即sit in the sitting room,所以不能填which,只能填in which或where.
3.All是先行词,在定语从句中作主语,只能填that.A选项要说成the things that才对,that绝对不能省略,因为all the things在定语从句中作主语的,that不能没有.但是下面这句话that就可以省略了：All __(that)__ he told me is true.这时all在定语从句中作宾语(told me all).
4.先行词a single person,在定语从句中是turn to a single person for help,所以要填to whom.
5.前半句先行词these years,在定语从句中I lived in the country with the farmers in these years是作时间状语的,所以要填when；
后面半句话的先行词不是the farmers,而是I lived in the country with the farmers这个句子.因为如果是the farmers的话,在后面的定语从句中的谓语动词不应该是has,因为the farmers是复数形式,至少要说成have a great effect...；而先行词是前半句句子（即“我和农民住在农村”的那件事）,在定语从句中作主语,要用which.
6.先行词this year,如果要选C (which),那么一定是在定语从句中作主语或宾语,但是定语从句中主语是their team,宾语是the World Cup,只能作时间状语(their team won the cup this year),所以要选D(when).
7.先行词是those,即those flowers,在定语从句中作主语(the flowers once grew in the forest),因此that不可省略,所以只能选C.