Through so much trouble，he learned everyone needed friendship and self confidence is impo

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A. that；/
B. /；/
(答案→)C. that；that
D. /；what
解析：考查宾语从句的连接词。     everyone needed friendship and     self confidence is important.是两个并列的宾从，从句都不缺成分，所以用that引导，第一个that可以省略，第二个不可少，所以选C。