The correct answer will be the third one. Nuclear families are generally smaller (Many of them only include parents and sons); extended families include families of the same grandparents(as uncles, aunts, cousins)
It's mainly a matter of opinion, but I'd say no.
I mean to my understanding yes, the scale the object was measured on may have dust particles on it, making the accurate measurement not completely precise, or maybe some things that were out of your control alter the measurement. I hope this helps:))
