Consider statements about human reproduction: 1. Fertilization occurs in the uterus. 2. The placenta nourishes the fetus. 3. Spermatogenesis occurs in the testes. Which are correct? MCQ with Answer and Explanation

Explanation:
Arthropoda is the largest phylum, with over a million described species, including insects, arachnids, crustaceans, and myriapods. They are characterized by jointed appendages, chitinous exoskeleton, and segmented bodies. Insects alone represent the majority of animal species. Chordata is comparatively smaller.

Explanation:
Vitamin K is essential for the synthesis of clotting factors (II, VII, IX, X) in the liver. Deficiency leads to prolonged clotting time and excessive bleeding. Vitamin A is for vision, C for collagen (scurvy causes bleeding gums but not clotting defect), D for bones. Newborns receive vitamin K injection to prevent hemorrhagic disease. Green leafy vegetables are rich sources.

Explanation:
Albert Sabin developed the attenuated oral polio vaccine (OPV), which is easier to administer and provides intestinal immunity. Salk developed the inactivated vaccine (IPV).