Which of these fits gap 17?

Directions: Complete this passage by selecting the most suitable option for the corresponding gap.
The coelacanth is a primitive fish that once ______(17)______ to be long extinct.
They are called living fossils because they have several body structures and adaptations that are _____(18)_____ in fossil fish and in no other living specimen.
They date _____(19)_____ the Devonian Period of the Earth that is at least 350 million years old.

They ______(20)_____ the deep sea and are found in small numbers below a depth of 200 meters in the Indian Ocean.