A bitter pill to swallow means an unpleasant fact or result that is difficult to accept. The correct answer is this meaning because the expression is used figuratively, not only by its literal words.

Examples:

• Losing the final after months of practice was a bitter pill to swallow.
• In an HSC essay, A bitter pill to swallow can express this meaning: an unpleasant fact or result that is difficult to accept.
• When this expression appears in a passage, connect A bitter pill to swallow with the idea of an unpleasant fact or result that is difficult to accept.