Final answer:
The structure formed in the ovary from the follicle of an ovulated oocyte is the corpus luteum, which plays a crucial role in the menstrual cycle and early stages of pregnancy.
Step-by-step explanation:
After ovulation, the follicle that released the oocyte transforms into a structure known as the corpus luteum. The process of folliculogenesis involves the development of ovarian follicles from primordial to tertiary under the stimulation of gonadotropins such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The granulosa cells of the ruptured follicle luteinize and begin to produce progesterone, thus forming the corpus luteum. This structure is essential as it supports the potential early stages of pregnancy by maintaining the uterine lining. Therefore, the correct answer to which structure is formed in the ovary from the follicle of an ovulated oocyte is (a) Corpus luteum.