The statement which contains an ironic use of understatement is: The pilot called flying from one side of the Atlantic to the other a simple task of "puddle jumping." So, the right answer over here is Option D.
<u>Explanation</u>:
When an author or a writer wants to make a situation seem lessimportant or significant than it truly is then he/she makes an understatement. This figure of speech offers an ironiceffect to a statement and results in saying something opposite than what is expected. In this statement mentioned above, the Atlantic ocean is ironically described as a puddle but it actually means that the Atlantic ocean is gigantic.