Explanation:
To solve for the number of terms (\(n\)) in the arithmetic progression, we can use the formula for the sum of the first \(n\) terms:

\[
S_n = \frac{n}{2} \times (a + l)
\]

Where:
- \(S_n\) is the sum of the first \(n\) terms
- \(a\) is the first term
- \(l\) is the last term
- \(n\) is the number of terms

Given:
- \(S_n = 252\)
- \(a = -16\)
- \(l = 72\)

Substituting the values into the formula:

\[
252 = \frac{n}{2} \times (-16 + 72)
\]

Simplifying:

\[
252 = \frac{n}{2} \times 56
\]

Multiply both sides by 2 to eliminate the fraction:

\[
504 = 56n
\]

Solve for \(n\):

\[
n = \frac{504}{56} = 9
\]

Thus, the number of terms in the series is D. 9.