According to Pi, a zookeeper will know he or she has created a healthy environment for the animals WHEN THE ANIMALS REPRODUCE.
For animals to reproduce and give birth to young ones, many things has to be in place, such as suitable partners, right environment, right food, etc. Animals naturally reproduce when the environment is favorable unto them. Thus, reproduction of animals in the zoo shows that the right environment has been created for the animals.
Inflecting run to running changes the word would into a {ANSWER adverb} hope this helpds :*)
A. Most lines use iambic pentameter, which doesn't resemble the way we speak now.
