I don’t think Germany will win the World Cup three years from now.

A．after three years

B．the third year

C．in three years

D．three years later

某有机物B的分子式为C₄H₄O₄，其结构简式为HOOCCH=CHCOOH

（1）B分子所含官能团的名称是            、               。

（2）1mol C₄H₄O₄完全燃烧需消耗O₂ __       __ mol。

(3)与B的具有相同官能团的同分异构体的结构简式是                。