The hormone that stimulates the thyroid gland to secrete thyroxine is: MCQ with Answer and Explanation

Explanation:
Innate immunity is the non-specific defense mechanism present by birth, including physical barriers and phagocytes. Vaccination introduces antigens to stimulate the body's own antibody production, conferring artificial active immunity. Antibodies (immunoglobulins) are produced and secreted by B-lymphocytes (plasma cells), not T-lymphocytes, which are involved in cell-mediated immunity. Thus, statements 1 and 2 are correct.

Explanation:
The ozone layer is in the stratosphere (15-35 km altitude), absorbing harmful UV-B and UV-C radiation. CFCs cause its depletion.

Explanation:
Bacteria exhibit diverse nutritional modes; some are autotrophic (photosynthetic like cyanobacteria or chemosynthetic), while others are heterotrophic (saprophytic or parasitic). Fungi are eukaryotic organisms, characterized by having a true nucleus and membrane-bound organelles, and are heterotrophic. Viruses are considered non-living outside a host cell because they lack metabolic machinery and cannot replicate independently; they only exhibit living characteristics inside a host. Thus, statements 1 and 3 are correct.