Final answer:
The unit equivalent to J/s is the watt (W), which measures power and is equal to the rate of energy transfer of one joule per second.
Step-by-step explanation:
The unit equivalent to joules per second (J/s) is the watt (W), which is the standard unit for power in the International System of Units (SI). The joule is a derived unit of energy, work, or amount of heat. When one joule of work is done in one second, it is equivalent to one watt. By extension, the watt measures the rate of energy transfer. We know that 1 watt = 1 J/s, meaning that the energy transfer at the rate of one joule per second is equal to one watt of power. Therefore, the correct answer to the student's question is D. Watts.