题目内容
Researchers have failed to find a way to treat such diseases, and it will still be years before they can find ____ is effective.
A. the one B. one that C. the one that D. one
B

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题目内容
Researchers have failed to find a way to treat such diseases, and it will still be years before they can find ____ is effective.
A. the one B. one that C. the one that D. one
B