Look at ______ skirt. I bought it for Mum on Mother's Day. Isn't it nice? [ ]

A. a

B. an

C. the

D. /

下列材料中为非降解性高分子聚合物的是（）

A.硅橡胶

B.聚四氟乙烯

C.羟基磷灰石

D.聚乳酸

E.钛合金