Correct Answer:
B. Cotton
A cash crop is an agricultural crop grown to be sold for profit, rather than for the subsistence of the farmer. Among the given options, Cotton is a prominent cash crop of Pakistan. It is a vital raw material for the country's textile industry, which is a major contributor to its economy and exports. While wheat, maize, and barley are also cultivated in Pakistan, they are primarily considered food crops, essential for domestic consumption, although surpluses can be sold. Cotton's primary purpose in Pakistan's agricultural economy is commercial sale and industrial use.