Which statement best expresses how the author achieves a particular purpose in paragraphs 5
and 6?
A The author describes the time it will take for spaceships to reach the nearest star to
explain why Nick Sagan's message will never be heard.
B The author builds an explanation of the limitations of a spaceship's speed as a
transition to a description of how warp speed theory works.
C The author contrasts various technologies that can increase a spacecraft's speed to
indicate the likelihood of reaching a nearby star in the future.
D The author includes unreasonable examples of how to increase a spacecraft's speed
to emphasize the unrealistic expense of such an endeavor.