Step 1: For the terms to be in A.P., the middle term must be the average of the first and third terms.
\[
13 = \frac{(2p + 1) + (5p - 3)}{2}
\]
Step 2: Solve for \( p \):
\[
13 = \frac{2p + 1 + 5p - 3}{2}
\]
\[
13 = \frac{7p - 2}{2}
\]
\[
26 = 7p - 2
\]
\[
28 = 7p
\]
\[
p = 4
\]
Thus, the correct answer is \( p = 4 \).