In the last 100 years, the level of co2 in the atmosphere has been significantly increased by man by: pesticides the burning of fossil fuels domestic heat incineration of waste products

The correct answer is Option (2)- Burning up of fossil fuels

Explanation:

Fossils are the remnants of the ancient plants and animals that were buried millions of years ago. Those fuels that are made up of these fossilized matters are commonly termed as fossil fuel. For example, Petroleum, Coal and natural gas. These are the major source of energy.

These fossil fuels are limited in amount and are non-renewable sources of energy. These are exploited rapidly by human beings. This burning up of fossil fuels leads to the production of a large amount of Carbon dioxide (CO₂) gas that causes a significant impact on the atmosphere. The increase in the CO₂ content also leads to an increase in the global temperature of the earth.

In the last 100 years, the CO₂ level in the atmosphere has immensely increased.

Hence, the correct answer is option (2).