The advantage of series-connections is that they share the supply voltage, hence cheap low voltage appliances may be used. Correct option is (A). 

Series vs Parallel Connections in Electrical Circuits

Cost efficiency is an important consideration when designing electrical circuits. Two common ways to connect electrical components are in series or in parallel. Let's compare the cost efficiency of these two types of connections.

Series Connections

In a series connection, the components are connected one after the other, so that the current flows through each component in turn. The total resistance of the circuit is the sum of the resistances of each component. The current is the same in each component, but the voltage is divided between them. For example, if two resistors of equal value are connected in series across a 12V power supply, each resistor will receive 6V.

Cost efficiency of Series Connection

Series connections are not cost efficient because:

- Higher resistance: The total resistance of the circuit is higher than the resistance of each individual component, which means that more power is wasted as heat.

- Lower voltage: The voltage across each component is lower than the supply voltage, which means that larger voltage rated components may be required, increasing cost.

Parallel Connections

In a parallel connection, the components are connected side by side, so that the current divides between them. The total resistance of the circuit is less than the resistance of each individual component. The voltage is the same across each component, but the current is divided between them. For example, if two resistors of equal value are connected in parallel across a 12V power supply, each resistor will receive 12V.

Cost efficiency of Parallel Connection

Parallel connections are more cost efficient than series connections because:

- Lower resistance: The total resistance of the circuit is lower than the resistance of each individual component, which means that less power is wasted as heat.

- Higher voltage: The voltage across each component is the same as the supply voltage, which means that smaller voltage rated components may be used, reducing cost.

Conclusion

In conclusion, series connections are not cost efficient because they have higher resistance and lower voltage, while parallel connections are more cost efficient because they have lower resistance and higher voltage. Therefore, the most cost efficient connection is parallel.

In series connection currents same in all resistors voltage will be different ,in parallel connection current will be different voltage same in all.thats why losses will be more in series ,losses will be less in parallel connection.parallel connection is efficiency