The correct answer is (d) Income Tax.
Income tax is a tax on the income of individuals and businesses. It is the largest source of revenue for the government of India. In the Union Budget 2005-06, income tax accounted for 36.9% of the total revenue of the government.
Corporate tax is a tax on the profits of companies. It is the second largest source of revenue for the government of India. In the Union Budget 2005-06, corporate tax accounted for 23.6% of the total revenue of the government.
Excise tax is a tax on goods and services. It is the third largest source of revenue for the government of India. In the Union Budget 2005-06, excise tax accounted for 17.4% of the total revenue of the government.
Customs tax is a tax on goods imported into the country. It is the fourth largest source of revenue for the government of India. In the Union Budget 2005-06, customs tax accounted for 12.1% of the total revenue of the government.
The government of India also collects revenue from other sources, such as service tax, stamp duty, and non-tax revenue. However, income tax, corporate tax, excise tax, and customs tax are the four main sources of revenue for the government of India.