Through a process called photosynthesis, leaves pull in carbon dioxide and water and use the energy of the sun to convert this into chemical compounds such as sugars that feed the tree. But as a by-product of that chemical reaction oxygen is produced and released by the tree.
For double confirmation, I also took the quiz on Edge!
This is true It has happened before and was one of the factors that influenced the current position of the continents. It will surely happen again if one day an ice age happens.