Final answer:
The statement is true as Islam was primarily established in the Arabian Peninsula by A.D. 632, under the leadership of Prophet Muhammad, before expanding rapidly into surrounding regions.
Step-by-step explanation:
The statement that Muslim lands in A.D. 632 consisted mainly of the Arabian Peninsula is true.
Early in the seventh century, Islam was founded by the Prophet Muhammad in the region of Mecca on the Arabian Peninsula.
By the time of his death in 632, Islam had been well-established in the eastern Arabian Peninsula.
After his passing, Islamic armies rapidly expanded the Muslim realm, but the initial territory under Islamic rule was primarily the Arabian Peninsula.