Question

Only those ______ knows well could be let in.

A. who
B. he
C. that
D. what

Answer 1

答案B
句子顺序为：先行词(those)+引导词（that/who，作宾语时可省）+主语+谓语部分。由此可知句子缺少主语，故用he作定语从句的主语。