The blood group known as the universal donor is: MCQ with Answer and Explanation

Explanation:
Rhodopsin (visual purple) in rod cells of the retina consists of opsin and retinal (derived from vitamin A). It bleaches in light, triggering nerve impulses. It is highly sensitive, enabling night vision. Iodopsin is in cones for color vision.

Explanation:
TSH, released from the anterior pituitary, binds to receptors on thyroid follicular cells, stimulating the synthesis and release of thyroxine (T₄) and triiodothyronine (T₃). TSH release is regulated by thyrotropin-releasing hormone (TRH) from the hypothalamus and feedback inhibition by thyroid hormones. ACTH stimulates adrenal cortex, GH growth, prolactin milk production.

Explanation:
Immunoglobulin G (IgG) is the most abundant antibody in blood plasma, providing long-term immunity and crossing the placenta. Immunoglobulin E (IgE) is present in small amounts and binds to mast cells, triggering the release of histamine during allergic reactions. Immunoglobulin A (IgA) is predominantly found in mucosal secretions like saliva, tears, and breast milk, providing localized mucosal immunity. All statements are correct.