[单选题]
The volume of the Ear3(l;,-;w jf*zji9z0jllipsp v 9wg v ety4a(s)h 4 rgvth is approximately $10^{12} \mathrm{~km}^3$ and the volume of a grain of sand is approximately $1 \mathrm{~mm}^3$. To the nearest order of magnitude, if the Earth was hollow, how many grains of sand could it contain?
A. $10^{12}$
B. $10^{18}$
C. $10^{24}$
D. $10^{30}$
Post time 2024-8-21 21:17:15