Final answer:
Sphere 2 will reach air temperature first due to a higher surface area-to-volume ratio, which facilitates faster heat exchange.
Step-by-step explanation:
Considering two solid copper spheres, 1 and 2, where sphere 1 has twice the diameter of sphere 2, the sphere that will reach air temperature first when placed in quiescent air at 25°C from an initial temperature of 0°C is sphere 2, option B. This is due to the sphere's geometry and the rate of heat transfer. In thermodynamics, smaller objects with a higher surface area-to-volume ratio can exchange heat more quickly than larger objects with a lower ratio. Since sphere 2 is smaller, it has a relatively larger surface area-to-volume ratio compared to sphere 1, allowing it to reach thermal equilibrium with its surroundings faster.