摘要
84.in vain徒劳;白费All he had done was in vain at last.他所做的一切最终都是徒劳无功。85.on an average平均;按平均数计算1)The harvest is better on an average.收获按平均计比往年好。2)On an average,there are 1000visitors a day.平均每天有一千名游客。[同义]on the average与on an average同义86.on board在船上1)Who are those men coming on board?那些要上船的人都是谁?
