单项选择题
Course directed by the OSC or CSS to be steered at the beginning of a search is（）.
A.original course B.initial course C.final course D.designated course
单项选择题 Changing rescuers while carrying out artificial respiration should be done（）.
单项选择题 An uncontrolled flow of gas，oil，or other well fluids into the atmosphere is called a（）.
单项选择题 All the traces are（）old ones.
