Ascale drawing has a ratio of 100: 1. what does this ratio mean?
a. every 100 cm of the drawing equals 1 cm of the actual object
b. every 1 cm of the drawing represents 100 cm of the actual object
c. every 100 cm of the drawing represents 1 cm of the actual object

This ratio means that B. every 1 cm of the drawing represents 100 cm of the actual object.
Take Google maps for example - on the Internet, you see a small map of an actual place, and each centimeter or meter is proportional to some kind of measurement in actual nature. In these kinds of scales, the ratio is actual to model, not the other way round.