The land in Mexico City is subsiding over time. What is the primary cause of this problem? A.
too many dams being built along rivers
B.
deforestation caused by cutting down trees
C.
too many buildings being constructed
D.
underground aquifers being overpumped

Determine whether the following statements are true and give an explanation or counterexample. bold a. when using the shell method, the axis of the cylindrical shells is parallel to the axis of revolution. bold b. if a region is revolved about the y-axis, then the shell method must be used. bold c. if a region is revolved about the x-axis, then in principle it is possible to use the disk/washer method and integrate with respect to x or the shell method and integrate with respect to y.