Reincarnation best describes one of the major beliefs of Hinduism out of the above listed choices.
Hinduism is a polytheistic religion, and as such, can not be described in a monotheistic framework.
Hinduism is tied into the caste system, which is a hierarchical social classification, and, as such, egalitarianism can not be an essential element of Hinduism.
Stoicism, the endurance of pain without outward expression, was a large part of a Hellenistic philosophy, which was not religiously-based.
Reincarnation, the belief that souls are born again into different bodies (both human and non-human) is central to Hinduism. Reincarnation continues until the soul reaches an ultimate state of enlightenment. What being a soul is born into depends on how the soul behaved in the previous incarnation of life. Therefore, one is encouraged to live a kind and good life in order to be reincarnated into a desired form, and ultimately to escape the cycle of reincarnation.