The specific factor that is most likely responsible for the low annual precipitation at location C is its location in the center of a land mass away from any large bodies of water.
Large bodies of water act as moisture reservoirs, and they release moisture into the atmosphere through evaporation. Locations that are far from water bodies have fewer sources of moisture, which can lead to lower precipitation rates.
Therefore, the most likely explanation for the low annual precipitation at location C is its inland location, far from any large bodies of water. This location contributes to a drier climate due to the limited availability of moisture, subsidence of air masses, and reduced convectional rainfall.