Based on the tax system specification as described below, using boundary value analysis, which would...

Test set (i) is the best option as it tests the boundary condition of a salary of less than €20,000 and being married, with a varying number of children including the boundary value of three children. This test set covers the minimum and maximum values for the salary and the number of children, as well as the nominal values. The other test sets donot test the boundary value of the salary or the number of children fully, as they either omit or repeat some values. References =

ISTQB Certified Tester Advanced Level Syllabus Technical Test Analyst1, page 2

Boundary Value Analysis and Equivalence Partitioning Testing2, section “Boundary Value Analysis”

Equivalence Partitioning Method3, section “Example 1: Equivalence and Boundary Value”