In Which Example Would One MOST Likely See a Steady

Multiple Choice

In which example would one MOST likely see a steady rate of responding without any noticeable pauses?

A) A charitable organization receives a donation for every 10 phone calls it makes on average.
B) A teenager receives an allowance every Saturday.
C) A college student gets a call from home every Friday morning.
D) A blueberry picker receives $1 each time he fills three boxes.