Topic: Word Meaning, Subject: English Grammar (ইংরেজি গ্রামার)

Best Answer Explained in Below-:

The phrase "come across" means to encounter something or someone by chance, aligning perfectly with the idea of "happen to meet." For example, if you say you "came across" an old friend in a café, it suggests that you unexpectedly encountered them without prior arrangement. This term captures the spontaneity of meeting someone unexpectedly.

In contrast, the other options do not convey this same meaning. "Come round" typically refers to visiting someone or changing one's opinion, "come up" can mean to arise or occur, often in a scheduled context, and "come out" generally pertains to becoming visible or being released, neither of which imply a chance encounter. Therefore, "come across" is the most appropriate choice, as it explicitly denotes the accidental meeting aspect, making it the best match for the given question. Understanding the nuances of these phrases clarifies why "come across" uniquely represents the concept of an unexpected encounter.