Cell wall I'm pretty sure
Trees are not at fault for releasing greenhouse gas. Rather, they are the natural way of absorbing the gas in our atmosphere and are our primary natural ally.
Gravity is the attractive pull between two objects that have mass. The strength of gravity is directly proportional to the amount of mass of each object. ... An object with twice as much mass will exert twice as much gravitational pull on other objects. The gravitational force increases as the size of an object increases
