I want to challenge them

想───Think about it;挑战───Challenge

Go away and think about it, then let me know.───到一边去想一想，然后再告诉我。

When you think about it, he's probably right.───现在想想看，他很可能是对的。

He took a risk, I'll grant you. But when you think about it, the risk was pretty small.───我承认他有些冒险，但是回过来想一想，其实风险并不大。

Think about it very carefully before you decide.───仔细考虑一下再作决定。

He wanted to think about it -- to ponder over it, to decide whether it were best.───他要好好想一想 -- 仔细地考虑一下, 决定这是否是上策.

Give me a few hours to think about it.───给我几个小时考虑一下。

What do you really think about it?───你到底对这事怎么看？

I tried not to think about it. I blacked it out.───我尽量不去想它，竭力要将它忘掉。

What do you really think about it?

Just think about it.

I've had a long, hard think about it.

What do you think about it?

Let me think about it.