Canceling units is also called:

a. changing the value

c. multiplication

b. unit analysis

d. making connections

Cancelling or converting units is also known as (b) Unit analysis or "dimensional analysis", it is based on the principle that multiplying by the number 1 gives the same value, whereas dividing by the same value equals 1; this is a useful technique. When converting betwen units you're usually given one measure and asked to convert it to another measure.