解释如何检查它们是否正常运行，以及如何识别故障。

A.Explain check them whether normal or not, and how to identify a fault.

B.Make clear that if they operate properly and how to isolate the malfunction.

C.Explain how to check them for proper operation and how to recognize a malfunction.

正确答案：C

Basically, writers can use the approved words in the dictionary as a core vocabulary.

Make sure that there are safety barriers around the engine exhaust area.

If the filters become clogged after an unusually short time, send them to the laboratory for analysis of the contamination.

Put the mask on and breathe through it to make sure that the oxygen supply is correct.

If you cannot install the rigging pin easily, adjust the length of the rod.

Tighten the turnbuckle until you have the correct tension in the cable.

Do not operate the brakes to decrease the pressure in the accumulators.

The tension in the cables decreases if the temperature increases.

The warning bell and the horn must start and then stop again.

If the wheel temperature increases to more than 177 deg., the core of the fusible plug melts and the tire deflates.