Literal language uses words exactly according to their proper meaning or precise definitions.
Green is another term for being inexperienced, so George did not want to seem inexperienced.
The correct answer would be:
b. The mandate to marry within one's tribe
In the passage line : "If it had occurred to him that never in the history of his people had a man married a woman who spoke a different tongue, he might have been less optimistic. " It clearly shows how it has never happened that someone in the tribe marries someone form the outside, cause culturally in his tribe the mandate is to marry people from the inside.
It means that you are aware and are paying attention.
