— Did you go to the open-air concert?

— No. We ____. but we spent too much time shopping. [ ]

A. could have gone

B. must have gone

C. can't have gone

D. shouldn't have gone

下列关于2008年北京奥运会所用材料中，属于天然有机高分子材料的是（　　）

A．用羊绒为外层材料制作吉祥物-“福娃”

B．用轻薄高品质铝合金制作奥运会火炬-“祥云”

C．低合金高强度钢材铸造国家体育场-“鸟巢”

D．用ETFE膜（聚四氟乙烯一乙烯共聚物）建造国家游泳中心-“水立方”