helpful 
英 [ˈhɛlpfʊl]  美 [ˈhɛlpfəl] 
adj. 有帮助的，有益的；愿意帮忙的

例句：
None of these suggestions is very helpful. 

这些建议没一个有用。

The following information may be helpful to readers. 

以下信息可能会对读者有帮助。

I don't think it's very helpful to speculate at this stage. 

我认为现阶段揣测意义不大。

He could be really helpful in getting you a promotion. 

他对你的晋升可能确实会有很大帮助。