Their university is located on a beautiful lake, _____ of this developing city. [ ]

A. southeast thirty miles

B. thirty miles southeast

C. thirty miles to southeast

D. to thirty miles southeast

我国航天员在顺利完成首次空间出舱任务后安全返回，标志着“神舟七号”载人航天飞行取得圆满成功．航天员的装备是由我国自主研制的，其中头盔壳是用高强度聚碳酸酯制成的．已知聚碳酸酯的结构简式为

．下列说法正确的是（　　）

A．聚碳酸酯是通过加聚反应得到的

B．聚碳酸酯是纯净物

C．聚碳酸酯是通过缩聚反应得到的

D．它是体型高分子