Scenario The North American Beaver Is a Large Rodent That Builds

Scenario
The North American beaver is a large rodent that builds dams to convert freshwater streams into ponds. Beavers build their dams out of trees, which they cut down using their front teeth. Beavers also eat the leaves and bark of trees, as well as the starchy roots of water lilies.
-Beavers dams are sturdy, because the part of a tree that provides structural support when the tree is alive lends its strength to the dam, even after the tree is dead. What part of a tree provides this structural support?

A) heartwood
B) bark
C) collenchyma
D) parenchyma