Quizztime: old question in a new form:)

None of you answer my queries.. so I wonder why I bother. Nevertheless, the teacher's ego in me won't rest, so here I go, once more, trying to jog your interest with an old question asked by me hunderd times and more..

Pranayama means expansion of prana. What does prana mean? Below some options:
1) Blood
2) Breath
3) Life Force
4) Vitality

And if you are an instructor and don't know the meaning, jump off a cliff pronto:)
Answer tomorrow!