The structure that prevents the backflow of urine from the bladder to the ureters is the: MCQ with Answer and Explanation

Explanation:
Lysosomes are membrane-bound vesicles packed with hydrolytic enzymes (proteases, lipases, nucleases) that digest macromolecules, old organelles, and engulfed pathogens. They maintain an acidic pH (about 5.0) for optimal enzyme activity. Peroxisomes detoxify peroxides, mitochondria generate ATP, chloroplasts perform photosynthesis.

Explanation:
The cell wall is porous and does not regulate entry; the plasma membrane is selectively permeable. Thus, the wall is freely permeable, and the reason explains it.

Explanation:
Vitamin C, chemically ascorbic acid, is a water-soluble vitamin essential for collagen synthesis, wound healing, iron absorption, and antioxidant function. Its deficiency causes scurvy (bleeding gums, weakness). Vitamin A is retinol, B₁ is thiamine, D is calciferol. Vitamin C is abundant in citrus fruits, guava, amla. It is heat-labile and easily destroyed by cooking.