How does the central nervous system first appear during embryonic development?

If you are caught in a flash flood, or sea water rushing your way, drive to the ground you can find. highest lowest nearest darkest

Ihave a really high metabolism and only weigh 70 pounds (13 almost 14). people always ask me two questions: do you ever eat and how do you eat so much and stay so skinny.i am worried that a high metabolism wont me forever. what are some safe steps i can take to maintain being fit. (also, i already work out i am a dancer so i get cardio a lot)

Witch form of birth control could people use without. altering hormonal systems or blocking sperm from fertilizing an egg