1.They came to a house,in front of which there is a tall tre

1.They came to a house,in front of which there is a tall tree.2.I have seen the teacher whom you talked with about your son.3.There are many students in our class,three of whom are foreigners.4.He have flown to many countries three of which are his favorite ones.5.Many houses had been set to fire,most of which were buried to ground.6.The apples were bought by uncle Wang,half of which have gone bad.第一句,和was比哪个好?第二句,用现在完成时行吗?with提到whom前边可以吗?能不能举几个介词提前产生歧义的例子?第三句,whom为什么不能换成them?第四句,主句用现在完成时合适吗?第五句,主句用过去完成时合适吗?第六句,先行词和定语从句不在一起可以吗?