a. Because there are some trees with more leaves than others, they have a larger Leaf Area Index and tend to produce more oxygen. Bigger trees also tend to have more leaves making size a factor in oxygen production as well. Douglas-fir, true fir, maple, beech, and spruce trees are just a few examples of these. Pine trees give off the least amount while oak and aspen trees are in the middle of this spectrum.
b .In addition, the time of year also determines how much oxygen a tree makes. Most trees only produce the gas in the summer and spring months because that's when they have leaves. But there are evergreen plants and ones with green stems that are able to give off oxygen in the colder months. [***The Living Urn***](https://www.thelivingurn.com/blogs/news/trees-make-a-difference) points out that mature trees give off more oxygen than smaller ones that haven't matured.
c. Top 5 Oxygen Trees – Produce High Oxygen in India are Bael, Banyan, Peepal, Neem and Arjuna.