阀门故障的主要原因是液压油污染。

The primary cause of valve failure is contamination of the hydraulic fluid.

The primary cause of valve failure is poisonousness of the hydraulic fluid.

The primary element of valve failure is contamination of the hydraulic fluid.

正确答案：A

在每根管子的开口端放一个堵头。

以60度增量逆时针转动调节器。

此工具是可选的。

按这个顺序执行称重程序。

The diagram shall be arranged so that the flow of the system can be traced with a minimum of effort.

Make sure that you do not connect words which are not related, because this will change the meaning of the noun cluster.

If your reader must know about a specific condition before the start of a procedure or work step, give this condition first.

Technical texts often contain long groups of words that have the function of one part of speech in a sentence.

Technical verbs are words that give instructions and information in specified technical and operational contexts.

When you replace a word, always make sure that the alternative you select does not change the meaning of the sentence.