Which characteristic would most likely identify a laptop processor that uses less power?

The characteristic that most likely identifies a laptop processor as using less power is the 45nm process size. This refers to the fabrication technology used to create the processor. A smaller process size, such as 45nm, allows for more transistors to be placed on a chip, which typically leads to higher efficiency and lower power consumption. Process sizes reduce not only the physical space needed for the circuitry but also decrease the amount of power required for the processor to function effectively.

Smaller transistors can switch on and off faster and require less voltage, contributing to lower power demands and improving battery life, which is especially crucial for laptops. In contrast, higher wattage specifications indicate greater power consumption: as seen, 125 watts and 90 watts represent power levels that are more typical of desktop processors than laptops. The L2 cache size does not directly correlate to power consumption; rather, it primarily influences performance and speed by providing quicker access to frequently used data.

Thus, the 45nm process size is the key characteristic associated with lower power usage in laptop processors.