Which of the following is NOT mentioned as civilian users of GPS a. Hikers. b. Bankers. c. Fishermen. d. Internet service providers.

泡沫玻璃是将空瓶、玻璃等废弃材料经碾碎、髙温烘灼制成的轻石状或板状的（）

A.准轻质材料

B.一般轻质材料

C.混合轻质材料

D.超轻质材料