How is temperature defined in scientific terms?

Temperature in scientific terms is defined as a measure of the intensity of heat. This reflects how much thermal energy is present in a system or substance, and it indicates how hot or cold that system or substance is. In thermodynamics, temperature plays a crucial role as it influences the direction of heat transfer between objects. Higher temperatures correspond to greater kinetic energy of particles in a substance, while lower temperatures indicate less kinetic energy.

The other options provide definitions for concepts that are not directly related to temperature. Air pressure is related to the force exerted by air molecules per unit area, but it does not measure heat. The quantity of fuel consumed pertains to energy usage, not thermal energy directly. The weight of a substance relates to its mass and gravitational force, which also does not define temperature. Thus, option A is the most accurate and relevant definition.