Choose the correct answer in each of the following questions:

Let a be the first term of the AP.

Here, d = −4

$a_{5}=-3$                           (Given)

$\Rightarrow a+(5-1) \times(-4)=-3 \quad\left[a_{n}=a+(n-1) d\right]$

$\Rightarrow a-16=-3$

$\Rightarrow a=16-3=13$

Using the formula, $S_{n}=\frac{n}{2}[2 a+(n-1) d]$, we get

$S_{10}=\frac{10}{2}[2 \times 13+(10-1) \times(-4)]$

$=5 \times(26-36)$

$=5 \times(-10)$

$=-50$

Thus, the sum of its first 10 terms is −50.

Hence, the correct answer is option B.