The correct answer is D. Soyabean.
Soyabean is a good source of protein because it is a complete protein, meaning that it contains all nine essential amino acids that the body cannot produce on its own. It is also a good source of fiber, iron, and calcium.
Pea is a good source of protein, but it is not a complete protein. It is a good source of fiber and vitamins A and C.
Pigeon pea is a good source of protein, but it is not a complete protein. It is a good source of fiber and iron.
Black gram is a good source of protein, but it is not a complete protein. It is a good source of fiber and iron.
Here is a table showing the protein content of different types of beans:
| Bean | Protein (g/100g) |
|—|—|
| Soyabean | 36.6 |
| Pea | 24.4 |
| Pigeon pea | 23.4 |
| Black gram | 24.3 |
As you can see, soyabean has the highest protein content of all the beans listed.