病例组慢性胃灼热的暴露率为()
A.(80×280)/(20×70)
B.80/150
C.20/300
D.20/280
E.(80×100)/(350×70)
参考答案:B
关于角膜,错误的是()
A.属屈光系统
B.有血管分布
C.易受损伤
D.位于眼球的最前部
E.透明
In a river subject to tidal currents,the best time to dock a ship without the assistance of tugs is().
A.at high water
B.when there is a following current
C.at slack water
D.at flood