How did the reputation of Mongol warriors help grow the Mongol Empire?

People wanted to join the empire to gain the wealth that Genghis Khan gave away to his loyal followers.
People wanted to join the Mongol military because soldiers were taught to read and write.
Genghis Khan forced local leaders to inform him about his empire and then sent soldiers to enforce the laws.
People were scared into cooperating by the Mongol warriors’ violent reputation.