Final answer:
Difficulties in controlling the budget by Congress are due to the President's veto power, influence of interest groups, and the complex multi-step budget process, making D) All of the above the correct answer.
Step-by-step explanation:
The difficulty for Congress to control the budget can be attributed to various factors.
These include the veto power of the President, which allows the President to reject legislation passed by Congress, including budgetary measures.
Another factor is the influence of interest groups which can sway or pressure lawmakers to fund specific programs.
Additionally, the complexity of the budget process also makes it difficult to control the budget, as it involves multiple steps, from the President's proposal to the appropriations process in the Congress which includes analysis, hearings, and compromise before a final budget is passed.
To answer the question, D) All of the above are factors that make it difficult for Congress to control the budget.