Which one possesses high protein content?
A. Spirulina
B. Glycine max
C. Arachis hypogea
D. Pisum sativum

Hint: Certain single-celled microorganisms are edible and are a substitute for food rich in proteins. These cells can be used as an alternative food source for humans.

Complete answer:
Spirulina is cyanobacteria or blue-green algae. Throughout the world, Spirulina is used as a dietary supplement as well as a protein source. It is also considered as a Single-celled protein or SCP, due to its high protein content. The cells have about sixty percent of the protein content. It is used as a solution for malnutrition as well as in addressing food security issues. Due to its high amount of protein in a single cell, it possesses high protein content.
Considering the other given options:
Glycine max is popularly known as Soybean. It is a plant that belongs to the legume species. It is a dietary supplement as it contains a high amount of vitamin B and various minerals. Even though it is a common source of protein, the content of proteins is not as high as present in Spirulina. Thus it is not the appropriate option.
Arachis hypogaea are commonly known as Peanuts, which belong to the legume family. The edible portion is its seeds, and has a good nutritional value, containing a high amount of essential minerals. Even though it supplies proteins on consumption, it is not as high as Spirulina. Hence it is not an appropriate option.
Pisum sativum is commonly known as the garden pea. It is a common food material and is rich in various minerals and vitamins as well as protein. But the protein content is not as high as in Spirulina. Thus it is not the right option.
Therefore from the above-given options, the most appropriate one is A. That is Spirulina contains the highest protein content.

Note: There are many advantages to the usage of single-celled proteins as food sources. Due to the very low content of fat, it can be widely used. Some of the cells are manipulated genetically to include essential amino acids. The requirements for cultivation are simple and easy.