Answer:
B) 7 cm
Explanation:
The length of diagonal AC satisfies the relation described by the Pythagorean theorem:
AC² = AB² + BC² = (6 cm)² +(2 cm)² = 40 cm²
The length of diagonal A F also satifies the relation described by the Pythagorean theorem:
A F² = AC² +CF² = 40 cm² + (3 cm)² = 49 cm²
Then that length can be found by taking the square root of AF²:
A F = √(AF²) = √(49 cm²)
A F = 7 cm