~んだろう (I wonder)

You think I'm a sucker, don't you.

"I wonder what's going on inside the cave? I really want to know." "I have no idea."

Come to think of it, I remember he was a dashing man — I wonder what he's up to.

Both parents have died — what will become of those children?

How on earth did she pick up such a wealth of knowledge about fish?

I wonder how long the storm will last.

What a chatterbox she is!

I wonder what'll become of her.

I wonder why she didn't tell him about that.