急..英语语法填空

急..英语语法填空
1.Deciding what present you should give someone is not easy.Many things must be considered such as _____ the person is interested in and how old he is.?
为什么空格处填what 后面有介词in 不是应该用how吗?which呢?请详细解释3者在这里的不行与行的地方,谢谢
2.In 1900 the world's use of paper was about one kilogram ____ each person in a year.
for和of 在这里的区别,为什么用for?为什么不能用of? 谢谢哦
3.We have learnt some of the most important facts of European history from record that ____ (keep) on parchment.
我知道填被动语态 were kept .但是我觉得填 have been kept 也可以,词数不限,你觉得呢?直接填过去分词kept可以吗?不行的话为什么呢?
再问个地方，再加5分给你，To my amazement ,.................如果用To my amazing可以吗？用动名词代替名词？这里amaze做什么成分？