"a single-celled organism extends its
cytoplasm around its desired particle and
brings the particle inside of itself.
essentially, the cell is consuming this
particle."
which term below means "cell eating"?
a. phagocytosis
b. pinocytosis
c. exocytosis

A single cell organism extends its cytoplasm around its desired particle and bring the particle inside of itself. The cell consuming the particle this 'cell eating' is known as PHAGOCYTOSIS

Explanation:

Single celled organism amoeba  don't have well developed digestion system as higher animals. They use their cytoplasm for these functions to perform.

PHAGOCYTOSIS-  By this process some cells eat/engulf their food or required particle. When any food particle is present near the amoeba. amoeba extends its plasma membrane with cytoplasm around the particle and trap the particle in a new vacuole. For digestion lysosomes fused with the vacuole containing  food particle and enzymes secreted to the vacuole and this way food particle digested.

PINOCYTOSIS-In pinocytosis cell wrap arround the liquid droplet instead of solid food particle. Cell extends its cytoplasm to engulf the liquid.

EXOCYTOSIS- This is the process to secrete the waste material out from the body after digestion. This is the excretion system of amoeba. In this process vesicles form containing waste of the cell and cytoplasm move in this way away from the vesicle and reached on the surface of membrane. In this way vesicles discharge on the outer membrane.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.