Which of these fits gap 18?

Directions: Complete this passage by selecting the most suitable option for the corresponding gap.
Christopher Columbus ______(17)______ by many to be the first European explorer to find the continents of America.
Columbus was actually looking for a sea route to Asia from Spain, when he _____(18)______ land in the Caribbean Islands.
He and his people named the Caribbean Islands as West Indies. They thought that they _____(19)_____ the western part of India.

In the United States, the second Monday of October is a colourful holiday, called Columbus Day, in _______(20)______ Christopher Columbus.