A study ________ in the U.S.A. in 1977 showed that the chemical ASA in aspirin could prevent a stroke.
A. carrying out B. carried out C. working out D. worked out
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A study ________ in the U.S.A. in 1977 showed that the chemical ASA in aspirin could prevent a stroke.
A. carrying out B. carried out C. working out D. worked out