The correct answer is option 'C', the Lok Sabha exercises greater power over the Union budget.

Explanation:
The Union budget is the annual financial statement of the government, which presents its estimated revenue and expenditure for the upcoming fiscal year. It is an important tool for the government to allocate resources and implement its policies. The budget is prepared by the Ministry of Finance and presented to the Parliament for approval.

1. Overview of the Indian Parliament:
- The Parliament of India is the supreme legislative body consisting of two houses: the Lok Sabha (House of the People) and the Rajya Sabha (Council of States).
- The Lok Sabha is the directly elected lower house of the Parliament, while the Rajya Sabha is the upper house representing the states and union territories.
- Both houses have specific roles and powers in the legislative process, including the approval of the Union budget.

2. Role of the Lok Sabha in the Union budget:
- The Lok Sabha has greater power over the Union budget as it has the final authority to pass the budget.
- The budget is presented in the Lok Sabha by the Finance Minister of India, who explains the government's revenue and expenditure proposals.
- Members of the Lok Sabha have the opportunity to discuss and debate the budget, raise concerns, propose amendments, and suggest modifications.
- The Lok Sabha can approve or reject the budget, and any amendments proposed by the Rajya Sabha can be accepted or rejected by the Lok Sabha.
- In case of a disagreement between the two houses, the Lok Sabha has the final say on the budget.

3. Role of the Rajya Sabha in the Union budget:
- The Rajya Sabha also plays a significant role in the budget process, but its powers are limited compared to the Lok Sabha.
- The Rajya Sabha can review and suggest amendments to the budget proposals, but it cannot reject or make changes to the budget without the approval of the Lok Sabha.
- However, the Rajya Sabha can delay the passage of the budget by proposing amendments or raising concerns, which can lead to further discussions and negotiations between the two houses.

In conclusion, while both the Lok Sabha and the Rajya Sabha have roles in the approval process of the Union budget, the Lok Sabha exercises greater power as it has the final authority to pass the budget. The Lok Sabha represents the will of the people through direct elections, and its decisions carry more weight in the budgetary process.