Question

complete the sentence.
in the early 1900s, most deaths in the united states were caused either by pneumonia or ______, which spread quickly in overcrowded cities.

influenza

by influenza

Explanation:

The sentence uses the structure "either by A or B", where B should parallel the noun phrase after "by" (pneumonia). "Influenza" is a noun that fits grammatically and contextually—both pneumonia and influenza were major causes of death in early 1900s US, especially in crowded cities.

Answer:

influenza