Option 1: Maize is not considered a cash crop in India. Maize is primarily grown as a food crop and is used for human consumption and animal feed.

Option 2: Gram is considered a cash crop in India. Gram, also known as chickpea, is cultivated for its seeds, which are used in various culinary dishes and for making flour. The demand for gram is high, both domestically and internationally, making it a profitable crop for farmers.

Option 3: Onion is not classified as a cash crop in India. While onion cultivation is widespread in the country, it is primarily grown for domestic consumption rather than for commercial purposes.

Option 4: Wheat is not considered a cash crop in India. Wheat is grown extensively in the country and is an important staple food. However, it is not typically cultivated for commercial gain.

Therefore, the correct answer is Option 2: Gram.