#### Answer

(b) 1.5 C

#### Work Step by Step

We can find the combination of capacitors 1 and 2 which are in series connection by using the relation
$\frac{1}{C_{12}}=\frac{1}{C_{1}}+\frac{1}{C_{2}}$
But $C_{1}=C_{2}=C_{3}=C$
$\implies \frac{1}{C_{12}}=\frac{1}{C}+\frac{1}{C}=\frac{2}{C}$
Or $C_{12}=\frac{C}{2}$
Now $C_{12}$ and $C_{3}$ is in parallel.
Therefore, $C_{eq}=C_{12}+C_{3}=\frac{C}{2}+C=1.5\,C$