The Following Table Shows the Enrollment in a Private College $S_{n}$

Multiple Choice

The following table shows the enrollment in a private college for the years 1996 to 2005. Interpret these figures as partial sums, $S_{n}$ , of terms of a sequence, $a_{n}$ , where $\mathrm{n}$ is the number of years since 1995 (so $S_{1}=3641, S_{2}=3663$ , etc.) .

Which of the following gives the change in enrollment between 1999 and 2000 ?

A) $S_{4}$
B) $S_{5}$
C) $a_{4}$
D) $a_{5}$