The correct answer is A, as it provides the highest level of boundary coverage using two-point boundary value analysis. Boundary value analysis is a black-box test technique that focuses on the boundaries of input and output partitions1. Two-point boundary value analysis is a variation of boundary value analysis that uses only two values for each boundary: one just below the boundary and one just above the boundary1. In this case, the boundaries are the balance ranges that correspond to different interest rates. Option A covers all four boundaries using two values for each boundary: $100.00 and $100.01 for the first boundary, $500.00 and
$500.01 for the second boundary, $1,000.00 and $1,000.01 for the third boundary, and $5.00 as an invalid value below the lowest boundary. Option B covers only three boundaries using one value for each boundary:
$100.00 for the first boundary, $500.00 for the second boundary, and $1,000.00 and $1,000.01 for the third boundary. Option C covers only two boundaries using three values for each boundary: $100.00, $100.01, and
$100.02 for the first boundary, and $500.00 and $999.99 for the second boundary. Option D covers only two boundaries using one value for each boundary: $100.00 for the first boundary, and $1,000.01 for the third boundary, and $5.00 as an invalid value below the lowest boundary. References: 1, Section 4.2.3