~んだよ (explanatory + emphasis)

What do you take me for?

Where in Japan is there a school that makes kids do army crawls in gym class?

I'm always looking only at you, you know.

I'm the type to get nervous, so I'm bad at speaking in front of people, you know.

Even I'm a bit of a bookworm, you know.

I'll hide and you find me, okay? Got it?

She wants someone to talk things over with, you know.

I'm not going to the library. But I'll take you as far as the station.

Mine's in the shop getting fixed right now.

I get up at six, you know.