The test taker in me says this is the safest.

But... in a real life situation I’d attempt to dig my vehicle out. I have chains. If I can move enough snow I can get out. If you sit you risk being covered with snow. If I couldn’t dig out I’d run the engine for a short time for warmth cut it off for a while then run it again and do this until I got rescued or morning came.

If I went to get my room mate, she’s been stuck for a while, our chance of survival would be slim because you wouldn’t be able to move that vehicle. We’d both be out in the snow storm. My vehicle would be buried by the time we reached it.