I'm at a loss for words.

I just don't know what to say.

I don't know if I have the time.

For some reason the microphone didn't work earlier.

I can only wonder if this is the same for everyone else.

I didn't know where it came from.

She's asking how that's possible.

Thanks for having explained to me at last why people take me for an idiot.

I don't know what you mean.

I don't know how to demonstrate it, since it's too obvious!

I wouldn't have thought I would someday look up "Viagra" in Wikipedia.

Why don't you come visit us?

I don't know what to do anymore.

It is inevitable that I go to France someday, I just don't know when.

You can probably guess what happens though.

I don't know if I still have it.

I was wondering if you were going to show up today.

You'd be surprised what you can learn in a week.

It would take me too much time to explain to you why it's not going to work.

Would you like something to drink?