Answer:
 d. all of the above
Step-by-step explanation:
All of the given choices contribute to the elevated level of carbon in the atmosphere. 
This is one of the leading cause of climate change. 
- Greenhouse emissions from the surface is a huge problem which originates from increasing the release of these gases into the atmosphere. 
- Carbon dioxide is one of the greenhouse gases, and it is the main component of the emissions. 
- Deforestation involves the removal of trees from the earth surface. 
- Trees naturally removes carbon from the environment. They use the carbon to manufacture their own food. 
- Human activities such as industrial processes, burning of firewood for cooking, etc. all contributes significant amount of carbon into the atmosphere.