Final answer:
The Khyber Pass was the route through which people migrated to the Indus River valley, which became the cradle of the advanced Harappan civilization.
Step-by-step explanation:
People migrated to the Indus River valley using the A) Khyber Pass. The Indus Valley, home to the Harappan civilization, became one of the great civilizations of the Bronze Age, where innovative urban planning and sophisticated agricultural techniques were developed. The Khyber Pass has played a historical role in facilitating migrations and invasions, including the entry of Islam into northern India when the Delhi Sultanate was established.