丁苯橡胶的结构简式为合成这种橡胶的单体应是 [ ]

①②CH₃-CH=CH-CH₃ ③CH₂=CH-CH=CH₂

④CH≡C-CH₃ ⑤    

A．①②    

B．④⑤    

C．③⑤    

D．①③

I don’t think the watch will ______ much. It is ______ ＄30 at most.

A．cost, worth　

B．worth, cost　

C．spend, worth

D．worth, spend