Option 1 (Beetroot): Beetroot is not a rich source of protein. Although it contains some protein, it is not significant enough to be considered a primary source of protein.

Option 2 (Potato): Potatoes are not a rich source of protein. They are primarily a source of carbohydrates, with a small amount of protein present.

Option 3 (Soybean): Soybeans are indeed a rich source of protein. They are considered a complete protein, meaning that they contain all the essential amino acids required by the body.

Option 4 (Wheat): While wheat does contain some protein, it is not as high in protein content as soybeans. Wheat is primarily a source of carbohydrates.

Therefore, the correct answer is option 3, Soybean. Soybeans are a rich source of protein, making them a valuable food source for individuals looking to increase their protein intake. Alert - correct answer should be option 3, Soybean.