Respuesta :
cavernous = large and dark space
In the word cavernous, you can see the word cavern and cave. A cave is a large opening that is usually dark depending on how far back you climb or walk into it. Even though storm drain would indicate water, the word cavernous has nothing to do with water. It also has nothing to do with animals. And while it is creepy to reach into a dark space, cavernous does not mean creepy.
phlegm = mucus
While many of the other options could technically be correct if you were basing it solely on the sentence and not the word phlegm. However, phlegm is mucus, so this is your only answer.