certain trees, in fact, produces only when fire heats them if the fire moves thick shrubs and undergrowth the water supply increases adding other plants and local animals fire. Also may kill predatory insects or pests that live on and damage otherwise healthy trees. which context clues points to the correct definition of undergrowth in the second sentence?

The phrase "if the fire moves thick shrubs and undergrowth" provides context clues for the definition of "undergrowth" in the second sentence. It suggests that undergrowth refers to vegetation that grows beneath taller shrubs or plants.