<em>"A concave lens is thinner at the center than it is at the edges."</em>
If this isn't on the list of choices, that's tough. We can't help you choose the best one if we don't know what any of them is.
Answer:
B...................
An aquifer is the most expected feature that is likely to be reach after drilling through the unsaturated zone. Aquifer has tendency to transform ground water to the surface through voids. The depth of aquifer varies.
