Correct Answer:
B. 9cm
The correct answer is 9cm. The area of a triangle is given by the formula: Area = (1/2) × base × height. We are given Area = 126 cm² and base = 28 cm. So: 126 = (1/2) × 28 × height = 14 × height. Therefore, height = 126 ÷ 14 = 9 cm. 7cm, 8cm, and 10cm are incorrect values that do not satisfy the formula. Therefore, 9cm is the correct answer.