According to the Dharmashastras, the duties prescribed for Vaishyas are engaging in trade. This means that option 2 is the correct answer. The Dharmashastras are ancient Indian texts that provide guidance on social and moral duties based on Hindu religious principles. Vaishyas are the third varna or social class in the Hindu caste system, traditionally associated with occupations related to agriculture, business, and trade. The primary duty of Vaishyas, as per the Dharmashastras, is to engage in business activities and contribute to the economy through trade. This duty highlights the importance of commerce and the role of Vaishyas in economic development.

Option 1, which suggests studying the Vedas, is not correct according to the Dharmashastras. The study of the Vedas is considered more relevant to the Brahmin varna, who are responsible for performing religious rituals and imparting spiritual knowledge. Therefore, option 1 is not one of the prescribed duties of Vaishyas.

In conclusion, the Dharmashastras prescribe that the primary duty of Vaishyas is engaging in trade, making option 2 the correct answer.