The correct answer is C. Butane and propane.
Butane and propane are both flammable gases that are commonly used in cooking. They are both colorless and odorless, but they are often mixed with other chemicals to give them a distinctive smell so that leaks can be detected. Butane and propane are both lighter than air, so they will rise if they are released into the environment.
Carbon dioxide is a colorless, odorless gas that is produced when organic matter decomposes. It is also a byproduct of respiration and combustion. Carbon dioxide is heavier than air, so it will sink if it is released into the environment.
Carbon monoxide is a colorless, odorless gas that is produced when carbon-containing materials are burned incompletely. It is a very dangerous gas because it can bind to hemoglobin in the blood, preventing the blood from carrying oxygen to the tissues.
Ethylene is a colorless, flammable gas that is produced by plants. It is used in the production of plastics, synthetic fibers, and other chemicals. Ethylene is heavier than air, so it will sink if it is released into the environment.
In conclusion, the correct answer is C. Butane and propane.