Most rivers have relatively gentle gradients in the headwaters and steep gradients in their downstream portions.
true / false.

False

Explanation:

Most rivers don't have gentle gradients in the upper course or headwaters, rather most rivers always have steep gradient in their upper course. The upper course of a river is known as the headwaters region. But in their downstream regions, most rivers usually have relatively gentle gradients.

the thirteen colonies are:

connecticut, delaware, georgia, maryland, massachusetts, new jersey, new york, new hampshire, north carolina, pennsylvania, rhode island, south carolina, virginia

d is the logical answer but im not a 100% sure