It was not until dark __________ he found __________he thought was the correct way to solve the problem．

It was not until dark         he found         he thought was the correct way to solve the problem.

It was not until dark _____ he found _____ he thought was the correct way to solve the problem．

It was not until dark _______ he found _______ he thought was the correct way to solve the problem.?

A. that; what B. that; that　?

C. when; what D. when; that?

It was not until dark _____he found _____he thought was the correct way to solve the problem.

A.that; what??????? B.that ; that?????? C.when; that?????? D.when ;what