Which phrase would best express a lack of certainty about Mr. Milton's social capabilities?

The phrase that best expresses a lack of certainty about Mr. Milton's social capabilities is the one that indicates uncertainty regarding his confidence in social interactions. By stating that he is "not confident in social situations," it suggests that there are reasons to believe he may struggle or feel insecure when interacting with others. This uncertainty about his social skills is clearly communicated, implying that his abilities may fluctuate or be questionable, thereby reflecting a lack of assurance in his social capabilities.

In contrast, stating that he is "often confused in social situations" suggests a specific struggle without indicating overall uncertainty, while "generally outgoing" conveys a positive social trait, which does not reflect uncertainty at all. Saying he is "normally evaluated in social situations" suggests assessment rather than uncertainty or capability. Therefore, the phrase regarding his lack of confidence most directly communicates the doubt regarding Mr. Milton's social capabilities.