Area of a trapezium = 1/2 × (sum of parallel sides) × height. So area = 1/2 × (35 + 43) × 7 = 273 square mm. A trapezium has two parallel sides, so first add those two sides, then multiply by the height, and finally take half. The height must be the perpendicular distance between the parallel sides. So the correct choice is 273 mm².