Answer: C
Volume of the sphere \[ = \frac{4}{3}\pi[(21)^3 - (7)^3] \text{ cubic cm} = \frac{4}{3} \times \frac{22}{7} [9261 - 343] \text{ cubic cm} = \frac{4 \times 22 \times 8918}{3 \times 7} \text{ cubic cm} = \frac{4 \times 22 \times 1274}{3 \times 7} \text{ cubic cm} = \frac{4 \times 22 \times 1274}{3} \text{ cubic cm} = \frac{112112}{3} \text{ cubic cm} \] \(\therefore\) Weight of the hollow sphere \[ = \frac{112112}{3} \times 30 \text{ grams} = 1121120 \text{ grams} = 1121.12 \text{ kilograms} \]
Volume of the sphere \[ = \frac{4}{3}\pi[(21)^3 - (7)^3] \text{ cubic cm} = \frac{4}{3} \times \frac{22}{7} [9261 - 343] \text{ cubic cm} = \frac{4 \times 22 \times 8918}{3 \times 7} \text{ cubic cm} = \frac{4 \times 22 \times 1274}{3 \times 7} \text{ cubic cm} = \frac{4 \times 22 \times 1274}{3} \text{ cubic cm} = \frac{112112}{3} \text{ cubic cm} \] \(\therefore\) Weight of the hollow sphere \[ = \frac{112112}{3} \times 30 \text{ grams} = 1121120 \text{ grams} = 1121.12 \text{ kilograms} \]