Twenty people were killed as the boat overturned in the storm.

Answer: Option B

Drowned : die through submersion in and inhalation of water.
Capsized : (of a boat) overturned in the water.
Lost : unable to find one's way; not knowing one's whereabouts.
Disintegrated : break up into small parts as the result of impact or decay.
Overturned : turn over and come to rest upside down.

Synonym of Overturned is Capsized