CharlesSmith,______wasmyformerteacher,retiredlastyear.
B
that 不能引导非限制性定语从句 , 可以用 which 和 who 引导 , 其中 , who 代替的先行词是人。句意为：查理 ?史密斯去年退休了 ,他曾经是我的老师。
Thenewdiscovery_______beofgreatservicetomankind.
The new discovery _______ be of great service to mankind.
At any rate I did not succeed _______ myself understood by you.
It rained hard yesterday, ______ prevented me from going to the park.