B. The value of pi helped them explain that Earth is a rotating sphere.
That would be radar.
This was a key battle between Britain's RAF (Royal Air Force) and the Luftwaffe, if the Germans would've won most likely Britain would've been German; and many different outcomes could've happened in the past.
But, since radar was invented, and the British employed it in their tactics; that along with the communication between them helped repel the attack in the Battle of Britain.
Answer:NATO was organized primarily to "halt the growth of Communism in Europe" but it was also meant to ensure world peace and that another event like WWII wouldn't happen again