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

The correct answer is: A. drowned.

To drown is to die from suffocation by immersion or submersion in water. It is a leading cause of accidental death worldwide.

The other options are:

• B. capsized: to overturn or turn upside down, especially in water.
• C. lost: to be unable to find or locate someone or something.
• D. disintegrated: to break up into small pieces or particles.

In the context of the question, the only option that makes sense is A. drowned. The other options are not relevant to the question.