Final answer:
China refused to help Persia, leading to the conquest of the Persian Empire by Muslim forces.
Step-by-step explanation:
In 638, Persia appealed to China for help against Islamic advances into their empire. However, three years later, Muslim forces had conquered the Persian Empire.
The outcome of Persia's appeal to China was that China refused to help Persia, leading to the conquest of the Persian Empire by Muslim forces.