1.选C
（1）
“It" is known to all that Willian had broken his promise "that"he would give us a rise.
这里"It"替代that引导的主语从句作形式主语.如果不用"it"作形式主语应该是如下形式：
"That" Willian had broken his promise is known to all .
（注：这里句中第二个"that"是引导同位语从句作“promise"的同位语,这么用虽然句子没错但关系词that重复,而且主谓之间不够紧凑,这就是为什么要把It放在句首作形式主语的原因）
如果句首用“as"那应是如下形式：
（2）“As ”is known to all ,Willian had broken his promise that he would work out the plan on time.
这里“as"作为关系词引导的是一个定语从句,主句主语前不能再有关系词.
就此句分析“as"与“it"的区别如下：
（1）中 "it"作形式主语替代后面的主语从句
（2）中 "as"作关系词引导一个定语从句.
2.选C.
I really don't know___I put my wallet
分析：句中Know缺宾语,名词,代词,名词从句都可以作句子的宾语.
名词从句做宾语,句子要用陈述语气.故A,B,D排除 选C.
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