What is the best black box test design technique for verifying the accuracy of this user story?

User Story: As a user I want to be able to calculate tax percentage based on amount of income.

What is the best black box test design technique for verifying the accuracy of this user story?
A . Statement testing – test all statements in income calculation.
B. User story testing – test that the user can enter an income amount and get a result.
C. State transition testing – test all states of income entry.
D. Equivalence partitioning – test with low, medium and high income.

Answer: D