If $w'(t)$ is the rate of growth of a child in pounds per year, what does $\int_{5}^{\,10} {w'(t)}\,dt$ represent?

A. The rate of growth of the child (in lbs/year) during his/her first five years of life.
B. The increase in the child's weight (in pounds) during his/her first five years of life.
C. The rate of growth of the child (in lbs/year) between the ages of 5 and 10.
D. The increase in the child's weight (in pounds) between the ages of 5 and 10.