Beause we cut down a lot of trees. Often, so many, that the health of a forest is irreparably damaged. A forest is not just a bunch of trees. It is a whole ecosystem, in which the trees anchor the growth of many other plant and animal species, hold the ground together to prevent erosion, and produce a lot of oxygen to support animal life. If you harvest too many of the trees, the local ecosystem stops being a forest and starts turning into something else
Muscles - they are meat, and animals will eat the meat. They also decompose, leaving no trace of the remains.
i think its D but i'm not 100% sure
