Why do Earth, Mars, and Venus lack any hydrogen and helium in their atmospheres?

Some of the hydrogen bonds with other elements, but most of it remains free hydrogen. Both hydrogen and helium are light elements, so they will tend to evaporate into space over time. ... But the gravity of Earth isn't strong enough, so Earth's early atmosphere of helium and free hydrogen evaporated into space.

Explanation:

endo:

regulates body hormones, aldosterone, vasopressin

neural:

signal, regulates body using electric signals, reflex

endo has to do with hormones; aldosterone and vasopressin are both hormones. i also had this question and got it right : d