Final answer:
The correct answer is option b) He's embarrassed by Lily's outburst.
Step-by-step explanation:
Gabriel's reaction to Lily becoming upset about the subject of men reveals that he is embarrassed by Lily's outburst. This is indicated by the fact that he colors as if he has made a mistake. His habits in relating to women and people of other social classes are not clearly revealed by this specific reaction, as it does not provide enough information about his overall behavior and attitudes.
Therefore, options a) He's secretly in love with Lily, c) He's a feminist, and d) He's indifferent to social issues cannot be determined from his reaction alone.