The exiles from the northern kingdom of Israel, after the Assyrian conquest in 722 BCE, largely assimilated into the Assyrian population. Many Israelites were taken to Assyria, while others were scattered. Over time, they lost much of their distinct identity, leading to the term "lost tribes of Israel." While some may have preserved aspects of their identity, the majority assimilated into the surrounding cultures. Thus, the most accurate answer among your options is:
assimilated into the Assyrian population.