Third choice "The ratio given is part to part. The total number of parts in the whole is 1 + 3 = 4." is the correct answer.
Step-by-step explanation:
We know that partitioning a directed line segment into a ratio of 1:3 means that we are dividing the given line segment into two parts whose first part is 1 times the of some quantity while the another part is 3 times of the same quantity. So basically we are comparing part to part in by ratio. And total number of parts in the whole will be just sum of both so we get 1+3=4
