Write a subtraction expression you can use to find the difference between the elevation at the top of the exosphere and the deepest point of the ocean.
a. Elevation at the top of the exosphere - Deepest point of the ocean
b. Deepest point of the ocean - Elevation at the top of the exosphere
c. Elevation at the top of the exosphere + Deepest point of the ocean
d. Deepest point of the ocean + Elevation at the top of the exosphere