usefulness

Badly written questions limit the usefulness of questionnaires.

问题设得不好，调查问卷的就会打折扣。

He has outlived his usefulness.

他已老而无了。

The report is of potential usefulness to the government.

这个报告可能对政府有。

I was persuaded of the usefulness of his new device.

我相信了他的新装置的实性。

The index adds appreciably to the usefulness of the book.

索引明显地增加了这本书的实价值。

The theory is of limited usefulness.

这个理论有限。

Not only it can decide solely the lamp usefulness, but also available in mends light, sidelight, top light and the use of foot light.

它既可作主光灯，也可作为补光、侧光、顶光、和脚光的使。