You are presented with the quiz "What is formed when calcite is dissolved?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "acavern is formed by carbonic acid in groundwater seeping through rock and dissolving limestone" and "limestone Limestone Limestone is a grey rock that is made of calcite". 

So, what's the best answer to the question?


 

   a cavern        