问题补充：
A new kind of drug to cure H7N9 bird flu by the scientists and they are hopeful that they will succeed in a couple of weeks.
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：句意：一种新的药物正在被科学家开发来治疗H7N9禽流感，他们希望他们会在几个星期后成功。从they are hopeful that they will succeed in a couple of weeks. 可知是正在开发，而且drug和develop是被被动关系，选B。
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