Final answer:
The best word to complete the sentence about Pocahontas having trouble living on the moon due to the lack of atmosphere is 'TENUOUS', describing the weak or slight atmosphere one would encounter on the moon.
Step-by-step explanation:
The word that best completes the sentence “When John Smith brought Pocahontas to his colony on the moon, she had trouble with because she wasn't used to living somewhere without an atmosphere” is A. TENUOUS. This adjective describes something that is very weak or slight, which is applicable to the nonexistent or extremely weak atmosphere one would expect to find on the moon. Acculturation might seem relevant, but it refers to the process of cultural change and adaptation, not to the physical difficulties associated with living in an environment lacking an atmosphere.