I think that is a great idea.

我认为这是个好主意。

That's a great idea, Ellie.

“这是个好主意，艾莉。”

This party is such a great idea!

这个聚会真是个好主意！

Planting a tree for your birthday is a great idea!

为生日种树是个好主意！

I already have a great idea about how to do that.

我已经有一个很好的主意来做这件事。

Going to the new shopping mall sounds like a great idea.

去新的购物中心听起来是个好主意。

Our teacher decided to start a girls' football team and I thought, What a great idea!

我们的老师决定成立一个女子足球队，我觉得这是个好主意！

I have a great idea.

我有一个很好的想法。

Ah, that's a great idea!

啊哈，这真是个好主意！

Och, that's a great idea!

哦，那是个好主意！