Which of the following rock formations likely existed before the development of a stack?
A) sea arch
B) mesa
C) alcove
D) butte

A) sea arch

Explanation:

A natural arch or sea arch can be defined as a natural bridge which forms with an opening underneath.  A natural arch or sea arch is formed when the stacks are subjected to erosion. A stack can be defined as the geological form that is formed by the water wave erosion due to vertical column. The sea arches form inland cliffs, fins and other forms.