题目内容
Discovering the chemical successfully during the experiment is really a happy thing, but it remains _____ whether it has any uses.
A. to see B. seeing C. seen D. to be seen
D
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题目内容
Discovering the chemical successfully during the experiment is really a happy thing, but it remains _____ whether it has any uses.
A. to see B. seeing C. seen D. to be seen
D