Final answer:
The correct answer is option a) Yes, it is safe.
Step-by-step explanation:
It is safe to let a latte macchiato cool down; however, the taste may change as the temperature affects the flavor profile and texture of the coffee drink. As the latte macchiato cools, the layers settle due to the differences in density and temperature between the milk and coffee. This can also affect the overall experience of drinking the latte macchiato. If you're looking to conserve energy or money, turning the thermostat down to the lowest level that prevents damage, such as freezing pipes, is usually beneficial, especially if a timer can warm the house before you return.
When adding cream to coffee, if you add it right before drinking, the coffee will likely be hotter than if you added the cream when initially poured; this is because the cream has a cooling effect, and the longer it is in the coffee, the more heat is lost.
Finally, the phenomenon of heat transfer can be observed in the context of conduction (holding a hot cup), convection (steaming milk), and radiation (reheating coffee in a microwave).