Land plants evolved long before any animals appeared on earth. when they came onto land, they needed ways to keep from losing water, to reach the sun, and to produce oxygen. they started to convert the atmosphere from carbon dioxide to oxygen. which of these is believed to be the common ancestor of land plants?

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.

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