—Does your grandpa often walk the dog after supper?

— Yes, _________ bad weather stops him.

A．unless

B．because

C．though

D．since

道路交通标志用的反光膜一般由( )等材料组成。

A．透明薄膜

B．胶黏剂

C．高折射率微珠

D．反射层