Consider the following plants:

1. Groundnut

2. Horse-gram

3. Soybean

How many of the above belong to the pea family?

The correct option is All three.

To understand why all three plants belong to the pea family, let us examine their botanical classifications step-by-step:

1. Groundnut (Arachis hypogaea):
Groundnut, also commonly known as peanut, is a legume crop grown mainly for its edible seeds. Botanically, it belongs to the family Fabaceae (commonly known as the legume, pea, or bean family) and the subfamily Faboideae.

2. Horse-gram (Macrotyloma uniflorum):
Horse-gram is a popular legume crop grown widely in dry agricultural areas. It belongs to the Fabaceae family. It is a climbing herb that bears pods containing edible seeds, characteristic of members of the pea family.

3. Soybean (Glycine max):
Soybean is a major species of legume native to East Asia, widely grown for its edible bean. Like groundnut and horse-gram, soybean belongs to the family Fabaceae and subfamily Faboideae, making it a true member of the pea family.

Since all three listed plants—Groundnut, Horse-gram, and Soybean—are members of the Fabaceae family, they all belong to the pea family. Therefore, the correct count is all three.