The correct answer would be D. Idiom
Answer:
The United States were in competition with the soviet Union on who would be able to rule the skies by be the first to enter the moon.
<em>The ability of the NACA not to recieve adequate funding and being under beauracatic bottleneck didn't afford them the opportunity to actualise their aim hence the reason why Soviet Union where the first to send a manned space ship to the moon.</em>
Explanation:
The second option is the answer because unlike other options, the commas and full stops are placed correctly