Consider the following plants :

Correct Option

The pea family is scientifically known as Fabaceae (or Leguminosae). It is a large and economically significant family of flowering plants, characterized by its members' ability to fix atmospheric nitrogen through a symbiotic relationship with root nodule bacteria. Many plants in this family are cultivated globally for their protein-rich seeds (legumes), fodder, or as green manure.

• Groundnut (Arachis hypogaea): Despite its common name, groundnut is botanically a legume and belongs to the Fabaceae family. It is notable for its geocarpic nature, where the flowers are pollinated above ground, but the pods develop underground.
• Horse-gram (Macrotyloma uniflorum): This plant is a drought-resistant legume widely cultivated in semi-arid regions. It is a member of the Fabaceae family and is valued for its nutritional content and its role in enriching soil through nitrogen fixation.
• Soybean (Glycine max): Soybean is a globally important legume crop belonging to the Fabaceae family. It is highly valued for its high protein and oil content, making it a staple in human and animal diets worldwide.

Since all three listed plants-Groundnut, Horse-gram, and Soybean-are members of the Fabaceae family, the correct option is 'All three'.

Incorrect Options

Options 1 (Only one), 2 (Only two), and 4 (None) are incorrect. As established, Groundnut, Horse-gram, and Soybean are all legumes and belong to the Fabaceae (pea) family. Therefore, stating that only one, only two, or none of them belong to the pea family is factually inaccurate.