Meaning: 'Subtle' means something that is not immediately obvious or is delicate in nature, indicating that the difference between heat and temperature is nuanced yet significant.

Wrong options:

• spittle: 'Spittle' refers to saliva or spit, which is irrelevant in this context and does not convey any meaning related to distinctions.
• brittle: 'Brittle' describes something that is hard but easily broken, which does not apply to the nature of the distinction being discussed.
• dismantle: 'Dismantle' means to take apart or disassemble, which is not relevant to describing the nature of a distinction.

Correct answer: contained

Explanation: The word 'contained' is appropriate as it refers to the energy that is held within a system, fitting grammatically and contextually with the definition of temperature in the sentence.

Meaning: 'Contained' means held or kept within something, indicating that temperature is determined by the energy that is held within a singular system.

Wrong options:

• retained: 'Retained' implies keeping something in possession, which does not accurately describe the energy's relationship to temperature as it suggests a more active holding rather than being simply present.
• sustained: 'Sustained' means maintained over time, which does not fit the context of describing how energy is defined within a system.
• remained: 'Remained' suggests something that stays in a place, which does not accurately convey the concept of energy being part of a system.

Correct answer: conversely

Explanation: The word 'conversely' fits well as it indicates a relationship of contrast, highlighting the opposite situation of lacking heat, which aligns with the context of the sentence.

Meaning: 'Conversely' means in an opposite way, indicating that the lack of heat leads to a decrease in temperature, contrasting with the presence of heat.

Wrong options:

• scarcely: 'Scarcely' means hardly or barely, which does not convey the intended contrast between heat and temperature.
• sparsely: 'Sparsely' refers to something being thinly dispersed, which does not fit the context of contrasting heat presence and absence.
• diversely: 'Diversely' means in various ways, which does not accurately reflect the relationship of opposition needed in this context.

Correct answer: operating

Explanation: The word 'operating' is suitable as it describes particles functioning or moving at the same rate, fitting grammatically and contextually with the concept of thermal equilibrium.

Meaning: 'Operating' means functioning or working, indicating that particles are moving at the same rate when thermal equilibrium is achieved.

Wrong options:

• dictating: 'Dictating' means controlling or commanding, which does not fit the context of particles moving at the same rate.
• devastating: 'Devastating' means causing severe and overwhelming shock or grief, which is irrelevant to the description of particle behavior in thermal equilibrium.
• fascinating: 'Fascinating' means extremely interesting, which does not apply to the mechanical process of particles moving at the same rate.