His efforts to improve the sales of this product have been very(help)_为什么
问题描述：
His efforts to improve the sales of this product have been very(help)_
为什么
答
helpful, 有帮助的意思
答
helpful
他的努力是有用的……缺形容词……所以是helpful
话说楼主怎么老是你……回答不动了……闪了= =
答
helpful
他对提高产品销量所做的努力非常有效