input: The following are multiple choice questions (with answers) about medical knowledge.   **Question:** After a T cell progenitor leaves the bone marrow, most of its development takes place in the thymus. It passes through several stages during its maturation. Positive selection is an important process during maturation of T lymphocytes, and it ensures the preservation of self-major histocompatibility complex (MHC)-restricted T cells. During which of the following developmental stages does a T cell undergo this process?   (A) Pre-T cell   (B) Double-positive T cell   (C) Single-positive CD4+ T cell   (D) Single-positive CD8+ T cell
output: ['(B) Double-positive T cell <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Pre-T cell  (B) Double-positive T cell  (C) Single-positive CD4+ T cell  (D) Single-positive CD8+ T cell <> possible answers', '  After a T cell progenitor leaves the bone marrow, most of its development takes place in the thymus. It passes through several stages during its maturation. Positive selection is an important process during maturation of T lymphocytes, and it ensures the preservation of self-major histocompatibility complex (MHC)-restricted T cells. During which of the following developmental stages does a T cell undergo this process? <> context']