This is the first study to compare the effects of the new drug with its side effects.A. be

问题补充：

This is the first study to compare the effects of the new drug with its side effects.

A. beneficial

B. specific

C. powerful

D. potential

答案：

(答案→)A. beneficial

B. specific

C. powerful

D. potential

解析： A. beneficial有益的，B. specific明确的，具体的，C. powerful强大的，D. potential潜在的，句意：这是第一个对比新药物的有效的一面和副作用之间的影响的研究。所以选A。