Question

why was the south vulnerable to a blockade by the north?
a. the north had a well-organized navy, while the south had no navy and few good ports.
b. the north had a much larger population than the south.
c. the north had a large manufacturing base to produce weapons, while the south was mostly agrarian.
d. the north had a larger railroad system for moving troops and supplies than the south.

Explanation:

The South relied heavily on trade (especially cotton exports) and had a very small, underdeveloped navy, plus limited major ports. The North's strong navy could easily cut off the South's maritime trade routes, making it vulnerable to blockade. Other options relate to land-based advantages of the North, not blockade vulnerability.

Answer:

A. The North had a well-organized navy, while the South had no navy and few good ports.