Final answer:
In the context of Marshall's Bicentennial Speech, ‘coalesced’ most likely means 'came together for a purpose,' aligning with the mentioned efforts of groups uniting to counter common enemies.
Step-by-step explanation:
The context of the excerpt from Marshall’s Bicentennial Speech suggests that the most likely meaning of ‘coalesced’ as it is used there is ‘came together for a purpose.’ This inference is based on the context given, indicating that groups, though having their differences, joined forces due to the necessity of overcoming a mutual challenge. The key phrase, ‘took steps towards working in concert despite their differences,’ supports this interpretation that they joined together with a shared goal. Therefore, the correct answer is D: came together for a purpose.