ANS:D - both(b)&(c)

The unit of power is the watt (W), which is equivalent to joules per second (J/s). So, the correct option is: both (b) and (c) The watt (W) is the standard unit of power in the International System of Units (SI). It is defined as one joule per second. Power is the rate at which work is done or the rate at which energy is transferred or converted. When one joule of energy is transferred or converted in one second, it is said to have a power of one watt. Mathematically, power (𝑃P) can be expressed as: 𝑃=𝑊𝑡P=tW​ Where:

• 𝑃P = power in watts (W)
• 𝑊W = work done or energy transferred in joules (J)
• 𝑡t = time in seconds (s)

So, when we say that power is measured in joules per second (joules/s), or equivalently, in watts (W), it means we are expressing how much energy is transferred or converted per unit time. For example, if a lightbulb has a power rating of 60 watts, it means the lightbulb consumes or emits 60 joules of energy every second.