There are doubts about the usefulness of these tests.这些试验是否有用，人们有所保留。I was persuaded of the usefulness of his new device.我相信了他的新装置的实用性.The index adds appreciably to the usefulness of the book.索引明显地增加了这本书的实用价值....
Usefulness includes the fact the negatives have been calibrated.所谓有用,是指在底片上要有标度.The theory is of limited usefulness.这个理论用途有限。The report is of potential usefulness to the government.这个报告可能对政府有用。There are doubts about the ...