The ocean basin (a) is covered by undersea mountains. (b) is mostly flat but features mountains and trenches. (c) has not been mapped sufficiently to be understood. (d) is an area of low pressure. The...

The ocean basin

(a) is covered by undersea mountains.

(b) is mostly flat but features mountains and trenches.

(c) has not been mapped sufficiently to be understood.

(d) is an area of low pressure.

The Ogallala Aquifer

(a) underlies several states.

(b) is being pumped at a high rate.

(c) is a source of fresh water.

(d) all of these