Determine the equivalent capacitance of the combination depicted in...

Let the left terminal be node $A$ and the right terminal be node $B$.

The left plates of the top and bottom capacitors are directly connected to node $A$.

The right plates of the top and bottom capacitors are connected to the top and bottom wires, respectively. These wires are joined together at the right end by a vertical wire and connected to node $B$. Thus, the right plates of both these capacitors are at the potential of node $B$.

The middle capacitor is connected between the top and bottom wires. Since both these wires are connected together at node $B$, both plates of the middle capacitor are at the same potential. Therefore, it is short-circuited and does not contribute to the equivalent capacitance.

The circuit simplifies to two capacitors, each of capacitance $C$, connected in parallel between nodes $A$ and $B$.

The equivalent capacitance is $C_{eq} = C + C = 2C$.