问题补充：
It is believed that a new kind of drug by the scientists and they are hopeful that they will succeed in a few months.
A. has been developed
B. is being developed
C. is developing
D. has developed
答案：
A. has been developed
(答案→)B. is being developed
C. is developing
D. has developed
解析： 考查时态和语态。主语drug和动词develop是动宾关系，所以要用被动语态，排除C,D；根据they will succeed in a few months，可知还没有开发出来，所以不能用现在完成时态，选B，正在被开发。
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