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 We don’t doubt _____ he will succeed in the research work.

A. that         B. whether           C. how         D. what

We don’t doubt _____ he will succeed in the research work.

A. that         B. whether           C. how         D. what

We don’t doubt _____ he will succeed in the research work.

A. that        B. whether           C. how         D. what

 We don’t doubt _____ he will succeed in the research work.

A. that         B. whether           C. how         D. what