人体氟的主要来源是()。
A.食物
B.饮水
C.空气
D.含氟牙膏
E.含氟漱口液
参考答案:B
This football game was _____________ our school _____________ their school.[ ]
A. between, to
B. between, and
C. on, to
D. on, and
某轮从(40°N,140°E)航行到(42°N,160°E),则应驶的恒向线航程为()。
A.925.5nmile
B.913.6nmile
C.908.5nmile
D.903.1nmile