George believes that Lillian is arrogant, because she is part of the LGP group. Because other members of the LGP group that George has met are arrogant, he believes that Lillian must be too. This is an example of:

The correct answer is: The fallacy of composition.

Explanation:

The fallacy of composition refers to the usually mistaken idea that an individual has in which because a component of a whole is a certain way, the whole is that very certain way, too. The fallacy of composition is a simplified, subjective generalization that individuals come up with where there is not enough proof that the statement being provided is real.

Thus, as George believes Lillian is arrogant because she is part of the LGP groups and George has met previous LGP members who are arrogant, he is assuming all LGP members are arrogant. George has fallen into the composition fallacy.