What was the most important reason the city of boston chose to fill in much of their swampy land and coastal areas? a. swamps are breeding grounds for mosquitoes and other disease-bearing insects. b. the original peninsula was prone to flooding. c. more land was needed for its growing population. d. the harbor was inaccessible under the original layout.

The correct answer is C. "More land was needed for its growing population".

Explanation:

When the city of Boston was established in 1630, the available land was only a small peninsula covering less than 800 acres. However, more land was needed as the population of Boston began to growth. In consequence, people of Boston began to fill in swampy land and coastal areas using the lands in the hills of Beacon Hill, which elevation is currently 60 feet lower than it was before Boston started their expansion.