Hint: For answering this question we must remember the definition of heat. Heat is the form of energy that is transferred between two substances at different temperatures.
Complete answer: Heat is a source of energy that is transferred from one body to another as a result of their temperature difference. If two bodies are brought together at different temperatures, energy is transferred from the hot body into the cold body , i.e., heat flows. Typically the result of this energy transfer is an rise in the temperature of the colder body and a decrease in the hotter body temperature but this is not always the case.A material can absorb heat without an increase in temperature by changing from one physical state to another, from a solid to a liquid through a melting process, from a solid to a vapor through a sublimation process, from a liquid to a vapor through a boiling process, or from one solid to another that is generally called a crystalline transition. The main distinction between heat and temperature is that heat is a source of energy and temperature which is a measure of the amount of energy in a body. During the 18th and 19th centuries, that explained. For example, if we place your hand around it, the temperature of a hot cup of coffee may feel hot. It's hot, because heat flows from the cup to the coffee. As per the International System of Units (SI) the heat being a source of energy has the unit Joule (J). Nevertheless, the British thermal unit (BTU) is still used in other cases , i.e. calorie. The default unit for the transferred heat rate is the watt W specified as one joule per second.And 1 kilojoule is equal to 1000 Joules. Hence option C, which is SI unit of heat, is both Joule and kilojoule is the correct answer.
So, the correct answer is “Option C”.
Note: While answering these types of questions we must remember the definition, formula and SI unit of heat and energy. In this question we saw that both Joule and Kilojoule are SI units of energy. And Kilojoule is 1000 Joules. So, for answering such questions we must remember these properties.