1.B.What
What...us + is + that...
What...us 是名词性从句,做主语；is...是复合句的谓语动词,that-是表语从句.
2.D What,道理和1一样.
如果用it作‘形式主语’就要用that-引导“主语从句",并移到句子后面,保持句子平衡：
It is well known to us that- = That- is well known to us.
= As is well known to us,many earth's...out.(Not:Which is well known to us,...)
= As is well known to us,getting up...health.
还可以说：
Many earth's...out,as/ which is well known to us.(Both as- and which- is OKay here.)
Getting up...health,as/ which is well known to us.
只要句子结构正确,或使用得当,都可以,表达相同的意思.