Use the sentence to answer the question.
certain trees, in fact, produce seeds only when fire heats them. if the fire removes thick shrubs and undergrowth, the water supply increases, aiding other plants and local animals. fire also may kill predatory insects or pests that live on and damage otherwise healthy trees.
Which set of clues best points to the correct definition of undergrowth in the second sentence?
"insects, pest, fire"
"insects, pest, fire"
"seeds, fire, animals"
"seeds, fire, animals"
"thick shrubs, plants"
"thick shrubs, plants"
"water supply"