Everybody has ______ responsibility to save water, if future generations are to enjoy _____    similar standard of living to the one we enjoy now.

A．the; /

B．a; a

C．/; the

D．a; the

烷烃

是单烯烃R和H₂发生加成反应后的产物，则R可能的结构有（　　）

A．4种

B．5种

C．6种

D．7种