I called the police but they weren't very helpful.
我叫了警察，但他们不太肯帮忙。
You'll find it helpful to talk things over with a friend.
把情况和朋友详细聊一聊，你会觉得大有帮助。
The people I spoke to were very helpful.
我交谈过的人都很肯帮忙。
It's natural to feel helpless against such abuse.
对这种虐待感到无能为力是自然的。
He lay helpless on the floor.
他无助地躺在地板上。
The audience was helpless with laughter.
观众情不自禁地大笑。