Answer:
A
Explanation:
Stalactites and stalagmites are formed by chemical weathering. Water dissolves the calcites in the rock of a cave roof and the calcite is deposited as strange and wonderful structures below.
(https://owlcation.com)
(hope this helps!
I believe the answer is D. The reason I said D is because the craziest party is describing have been.
It is verb type sentence ==> is your answer.
I hope this helps ≧ω≦
Sorry if wrong :-(