In the driest environments, we'll find __________.

In the driest environments, low moisture levels are characteristic. These environments often experience a significant absence of water vapor in the air, leading to lower relative humidity and consequently, less moisture available in the atmosphere. This condition is typical of arid or semi-arid climates where precipitation is minimal, and evaporation rates are high.

In contrast, high dew points indicate a level of humidity that is not found in dry environments; high temperatures could possibly occur but do not define dryness specifically, and high vapor pressures suggest a greater amount of moisture present in the air. Therefore, the defining feature of dry environments is indeed the low moisture levels, making that the correct choice.