Fact 1: Sinkholes are formed by precipitation. Fact 2: Eventually, the sinkhole collapses into cavern. Given the two facts above, what are formed by precipitation?

Pick your answer from: (1). streams.. (2). clouds. (3). Sediment. (4). caverns. (5). streams. (6). rivers. (7). watershed. (8). rocks.
Answer:
(4).