拜托大家帮解决一下这些定语从句选择（不用解释,

拜托大家帮解决一下这些定语从句选择（不用解释,
1.He has lost the key to the drawer____the papers are kept.
a.where b.in which c.under which d.which
2.Antarctic ____we know very little is covered with thick ice all the year round.
a.which b.where c.that d.about which
3.It was in 1969____the American astronaut succeeded in landing on the moon.
a.that b.which c.when d.in which
4.May the fourth is the day_____we Chinese people will never forget.
a.which b.when c.on which d.about which