During the time of manifest destiny, the addition of was highly desirable because it contained two of the three natural ports on the pacific coast.

California

Explanation:

Manifest Destiny was a doctrine that preached the belief that the United States should expand. Americans believed that by widening their borders, they would increase freedom. The term was coined by journalist John Louis O'Sullivan in the year 1845. It was very successful because it coincided with the time of the March to the West.

As has already been said, the fate of Manisfest preached the United States, so the addition of land to the American territory was extremely desirable. An example of this was the desire for the addition of California. The biggest interest in adding california was because this state contained two of the three Pacific Coast natural ports.

a and b because with the other three, they simplify to something else.