Were there ______ seals at the aquarium? [ ]
A. a lots of
B. some
C. any
D. lot
答案:C
蝗虫的气体交换靠腹部的( )
A.体
B.气孔
C.气管
D.口器
热水伴热天然气管线抑制天然气水合物的生成,系统仅需在()下进行热水循环。
A.高压
B.超高压
C.超低压
D.低压