Conditions cause air to be dry.
humid
warmer
cooler
none of the above

Cooler

Explanation:

The cooler air temperature reduces the capacity of air to hold the water vapors. Also, the lower temperature conditions do not favor evaporation of water from water bodies and the addition of water vapor to the air. This makes the air of the cooler conditions drier ones.

On the other hand, warmer air can hold more water vapor and feels humid. The higher temperature conditions also add water vapor to the air through the evaporation of water from the sea, oceans, river, etc. and makes the air humid.  

condenser is used to focus in the light microscope.