What common physical feature do charleston and boston share

Both Charleston and Boston are cities in the North Eastern region of the United States with easy access to the Atlantic Ocean; thus, they were very important during and after the colonial period (for commerce), and that's why they both have witnessed significant physical and economic development (urbanization and expansion/growth) throughout the years.

answer; ///i believe that the correct answer is (b); ///the candidate must be a native born american citzen;

the answer is a, salt plain