complete the text with a /an,the,or no article

this man is inside a cave he's ____professional caver but he's still feeling nervous why because _____cave is much bigger than it looks In fact it's ______deepest cave in the world it's called _____krubera cave and it's near _____black sea it is ______only cave on earth than is more than 2 km deep caves like this are fascinating places for _____explorers because there are always new parts to discover ​​