Which statement describes natural selection? it is the primary mechanism for evolution. it must act on structural traits. it acts to cause overpopulation. it causes learned skills to become heritable traits.

It is the primary mechanism for evolution. -describes natural selection.

This natural selection is a process which was first proposed by Charles Darwin and it states that the organisms which better adapt to their environment tend to survive and produce more offspring. This theory is now believed to be the main process that brings about evolution.

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.

the transfer for conduction is the heat transfering from the liquid to the spoon

the transfer for convection is the heat rising from the liquid to the air

the transfer for radiation is the heat going through the sides of the cup and to the air

at least that is what i would do