Which of the following are the two systems of mine ventilation?

The correct answer is the combination of blowing and exhaust systems. These two systems are fundamental to ensuring proper mine ventilation and maintaining safe working conditions underground.

A blowing system, also known as a supply or fresh air system, works by forcing fresh air into the mine workings. This process helps to dilute and remove harmful gases, such as carbon monoxide, and provides oxygen for the miners working underground. It's essential for preventing hazardous conditions that might arise due to the accumulation of those gases.

The exhaust system, on the other hand, is responsible for removing stale air, noxious fumes, and other contaminants from the mine environment. By effectively expelling this air outside, the exhaust system helps to maintain air quality and safety for miners.

Combining these two ventilation systems is crucial for creating a balance of fresh and clean air while eliminating dangerous contaminants, thus promoting safety and efficiency in underground mining operations.