The scientist who developed the first vaccine against polio was: MCQ with Answer and Explanation

Explanation:
Cytokinins are plant hormones that primarily promote cell division (cytokinesis) in the presence of auxins. They are also crucial in delaying senescence (aging) of leaves by helping to maintain protein and nucleic acid content, a phenomenon known as the Richmond-Lang effect. They are synthesized mainly in root apices.

Explanation:
The human heart is a four-chambered muscular organ consisting of two upper atria (receiving chambers) and two lower ventricles (discharging chambers), ensuring complete separation of oxygenated and deoxygenated blood. The lungs are a pair of spongy, air-filled organs located on either side of the chest, serving as the primary site for gas exchange (respiration). The brain, the control center of the nervous system, is encased and protected by the bony cranium (skull). All statements are correct.

Explanation:
Bacteria are unicellular prokaryotic organisms, characterized by the absence of a true, membrane-bound nucleus and other membrane-bound organelles. Fungi are eukaryotic organisms, possessing a true nucleus and membrane-bound organelles, and can be unicellular (yeasts) or multicellular (molds, mushrooms). Viruses are acellular, non-cellular entities; they consist of genetic material (DNA or RNA) enclosed in a protein coat (capsid) and lack any cellular structure or independent metabolic machinery. Thus, statements 1 and 2 are correct.