Comprehension:
Some words have been deleted in the given passage. Fill in the blanks with the given alternatives. Select the most appropriate option for each blank.

Polar bears roam the Arctic ice sheets and swim in that region's coastal waters. They are (1)______ strong swimmers, and their large front paws, (2)______ they use to paddle, are (3)______ webbed. Some polar bears have been seen (4)______ hundreds of miles from land, though they probably cover most of that (5)______ by floating on sheets of ice.