When jacob saw shadows of people behind him on the walls of the dark alley, his blood pressure increased and breathing rate sped up. these physical reactions were most directly regulated by his: ?

The answer is amygdala. This is the region of the brain that is responsible for emotional responses such as fear and anxiety. It is part of the limbic system and hence important in decision-making. It processes information and sends signals to the hypothalamus and other regions such as the locus coeruleus (that processes fear and panic as in this case).

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.