#### Answer

The best unit of measure to express the area of the wall of a room would be square meters.

#### Work Step by Step

Clearly, units of square kilometers would be too large to reasonably express the area of the wall of a room. Also, if we expressed the area of the wall of a room in units of square centimeters, we would need to use a huge number. Therefore, units of square centimeters are too small. The best unit of measure to express the area of the wall of a room would be square meters. The wall of a normal room is several meters wide and a few meters high, so units of square meters would be the best choice.