Which one of the following foods is not naturally rich in protein?

Which one of the following foods is not naturally rich in protein?

Green leafy vegetable
Lentil
Yoghurt
Egg
This question was previously asked in
UPSC Geoscientist – 2022
Green leafy vegetables are not naturally rich in protein compared to the other options.
While green leafy vegetables are excellent sources of vitamins, minerals, and fiber, their protein content is relatively low on a per-weight basis compared to legumes, dairy products, and eggs.
Lentils are legumes known for their high plant-based protein content. Yoghurt, a dairy product, is a good source of animal protein. Eggs are a classic complete protein source, rich in high-quality protein. For example, 100g of spinach might contain around 2.8g of protein, while 100g of cooked lentils contains about 9g, 100g of plain yoghurt about 10g, and a large egg (approx 50g) contains about 6g.