What phrase reflects uncertainty about someone's reaction to news?

The correct choice indicates a lack of certainty about how someone will respond to news. The phrase "There is no telling how he will" suggests that the speaker does not know what the person's reaction will be and acknowledges the unpredictability of the situation. This expression conveys that the outcome is uncertain, which aligns perfectly with the idea of uncertainty about someone's reaction.

In contrast, the other phrases imply some degree of certainty or predictability. For example, stating "There is no doubt how he will" suggests that the speaker is confident about the person's reaction. Similarly, "There is complete clarity on how he will" also indicates a strong belief that the reaction is known and understood. The phrase "There is anticipation of how he will" hints at expectation, but it does not encompass the uncertainty inherent in the question. Thus, the chosen phrase effectively captures the essence of uncertainty regarding someone's potential response.