He is . A. Element
B. Composite
C. Homogeneous mixtures
D. Heterogeneous mixtures

A. Element

Explanation:

He is a symbol of an element called helium. Helium is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas (gas whose atoms are not bound to each other). It's the first in the noble gas group in the periodic table. As we can see in the attached image, its atomic number is 2.

Helium is known for causing people to have a high-pitched voice after being inhaled. Because it is lighter than air, when you inhale it and try to talk, the sound waves travel faster through the lower-density gas, resulting in a high-pitched voice.

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.

lizards have adapted to life in the desert. some desert lizards have toes with spiny scales to them run across the sand without sinking. some use the sand to hide from predators, or to search for small animals that they prey upon.