Questions are based on the passage you have just heard.
第19题答案为
A.The difficulty of breeding electric fish. B.The medical importance of electric fish. C.How certain fish use electricity. D.How fish navigate.
参考答案:
答案解析:
第23题答案为
第23题答案为 A.They occur at regular intervals. B.They can withstand great heat. C.Th