The correct answer is - Burning trees releases huge amounts of carbon dioxide, which is a greenhouse gas.
The burning of the trees makes huge environmental problems of all sorts, and one of the biggest problems emerging from it is the increased amount of carbon dioxide released into the atmosphere, which contributes to higher global temperatures because it is a greenhouse gas that manages to trap more heat into the atmosphere. The trees are a vital part of the storage and control of the amount of carbon dioxide because they use the carbon for their functioning and release the oxygen, so they are one of the biggest storages of carbon dioxide. Once burned, they release huge amounts of carbon dioxide into the atmosphere which has previously been stored in them.