Sea waves erode a rocky headland into a sea arch. When the roof of the arch later collapses, the wall-like rock pillars left standing in the sea are called:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Stacks
Waves first hollow out sea caves, which grow into sea arches. Further erosion breaks the roof of the arch and only its walls are left standing in the sea; these are stacks.