1.Mary said she had been familiar with(已经熟悉了）the exchange students from Canada in her class(familiar)
2.Doctor Smith,whom you can turn to for help(你能向他求助）whenever you have problems that you can't deal with,is respected by all of us(turn)
3.The reason why I prefer travelling(为什么我更喜欢旅游）in foreign countries to staying at home is that.(prefer)
4.i think jack,who keeps reading(他一直在读小说）all day,needs to rest.(read)