Answer and Explanation:
a. The word "it" refers to the root of a tree, which remains even after the tree is cut (receives a knife blow) and is capable of spreading over the entire land (it grows slowly consuming the land), allowing the the tree grow again.
b. A simple knife blow is not enough to kill a tree, as it only cuts off the aerial part of it, leaving the entire underground part alive and ready to grow again.
c. "It" refers to the tree and its resilience, which is the quality that many beings have to renew and grow again even after a strong attack.