—It is reported that it will rain hard next Sunday. 

—_______. We're planning to go boating that day. [ ]

A. I don't think so

B. I hope so

C. I'm afraid not

D. I hope not

蜻蜓的稚虫生活在水中，通过鳃进行气体交换，其直肠鳃在发育过程中起源于（）

A．外胚层

B．内胚层

C．中胚层

D．无法确定