Question

a) in ancient times a sea had been replaced by land.
b) a forest had once grown there but had become submerged by water.
c) the area had been a sea until recent times.
d) a saltwater sea had changed to a freshwater lake long ago.

Explanation:

Rock layers are oldest at the bottom (layer 1) and youngest at the top (layer 11). Layers 1-5 contain marine fossils (trilobites, shells, coral, fish), showing the area was once a sea. Layers 7-11 contain land plant and animal fossils, showing the area later became land. This sequence proves the sea was replaced by land over time. Option B is wrong because the top layers are land, not submerged. Option C is wrong because recent layers are land, not sea. Option D is wrong as there is no evidence of a freshwater lake transition.

Answer:

A. In ancient times a sea had been replaced by land.