The watt (W) is the SI unit of power. We verify each option using standard physics formulas found in the NCERT text:

1. Joule/second: Power is defined as the rate of doing work ($P = W/t$). The unit is Joule per second ($J s^{-1}$), which is defined as a watt .
2. Ampere $\times$ Volt: Electrical power is given by the product of voltage and current ($P = VI$). The unit is Volt $\times$ Ampere, which equals a watt .
3. (Ampere)$^2 \times$ Ohm: Substituting Ohm's law ($V = IR$) into the power equation ($P = VI$) gives $P = I(IR) = I^2R$. The unit is Ampere$^2 \times$ Ohm, which equals a watt .
4. Ampere/Volt: This ratio represents $I/V$, which is the inverse of resistance ($1/R$). This quantity is known as conductance, and its unit is Siemens (S) or $\text{ohm}^{-1}$, not watt .