Which statement contains an ironic use of understatement?

Responses
A The boys were so exhausted after the long flight that they slept for hours.The boys were so exhausted after the long flight that they slept for hours.
B We watched the different floats of the parade pass by for what seemed like an eternity.We watched the different floats of the parade pass by for what seemed like an eternity.
C I studied so hard for the test, I almost memorized the information written on my note cards.I studied so hard for the test, I almost memorized the information written on my note cards.
D The pilot called flying from one side of the Atlantic to the other a simple task of "puddle jumping.

D The pilot called flying from one side of the Atlantic to the other a simple task of "puddle jumping.