Option 1: Goods and Services Tax (GST) is a major indirect tax in India that was introduced in 2017. It is levied on the supply of goods and services within the country. While GST has been an important source of revenue for the government, it is not the largest contributor to the Gross Tax Revenue in 2019-20 (BE).

Option 2: Corporation Tax is a direct tax levied on companies in India. It is based on their profits or income. This option is the correct answer as it states that Corporation Tax has the largest contribution to the Gross Tax Revenue of the Government of India in 2019-20 (BE). This implies that the revenue generated from Corporation Tax was higher compared to other taxes during this period.

Option 3: Customs duty is a tax imposed on goods imported into or exported out of a country. While customs duty contributes to the tax revenue of the government, it is not the largest contributor as stated in the correct answer.

Option 4: Union Excise Duties are taxes levied on the production or sale of specific goods and are collected by the central government. Although they contribute to the tax revenue, they are not the largest contributor as stated in the correct answer.

Therefore, the correct answer is