I like guys who aren’t too serious and who have a good sense of humor.这句先行词是guys,关系代词who.
I’d prefer someone who I have something in common with.先行词someone,关系代词who.
who I can talk easily.这也是前面i'd prefer someone主句的定语从句,先行词someone,关系代词who.
第二题
1.The girl who/that won the race is happy.
2.The student who/that sits next to me is from America.
3.The boy who/that fell from a tree is not badly hurt.
4.The man whose car was stolen called the police.
5.She told me her address which/that/X I wrote down on a piece of paper.
6.Monday is the day when/on which we will come.
7.That is the restaurant where /in whichI will meet you.
8.The town where/in which I grow up is small.
纯手打,