The sovereign debt crisis in Europe and the fiscal deficit crisis in the United States have triggered global attention on government debt. Although the overall level of fiscal deficit and debt of China's central government is within the control range, sufficient attention should be paid to various explicit and implicit local debt problems to avoid triggering public finance and financial risks. Please answer:

B1.1 Why is it necessary to control government budget deficit reasonably and effectively? Please explain in detail the positive and negative effects of budget deficit on a country's economic development. (10 points)