Answer: A. a cave
Step-by-step explanation:
A sinkhole is a hole that occurs on land due to disturbance of the soil and other causes. It looks like a big dip in the ground.
If you're unsure of how it looks, search "sinkhole" and you will be able to get the answer quickly.
Logically speaking, if this hole were to become larger through the natural processes of chemical weathering and erosion, it would form a cave.
Let's use the process of elimination:
B is wrong because a sinkhole happens on land.
C is wrong because a delta forms when deposits of weathering and erosion are piled at the end of a body of water.
D is wrong because a coastline has nothing to do with a sinkhole.
Therefore, the correct answer would be A. a cave.
Hope this helped!