Consider statements about plant anatomy: 1. Collenchyma provides flexibility. 2. Sclerenchyma cells are dead. 3. Parenchyma stores food. Which are correct? MCQ with Answer and Explanation

Explanation:
Body Mass Index (BMI) is a simple index used to classify underweight, overweight, and obesity. It is calculated as a person's weight in kilograms divided by the square of their height in meters (kg/m2). While it is a useful population-level screening tool, it does not directly measure body fat and may not be accurate for athletes or the elderly.

Explanation:
Nitrogen fixation is the conversion of inert atmospheric N₂ into ammonia (NH₃) by free-living (e.g., Azotobacter) or symbiotic (e.g., Rhizobium) bacteria, or by industrial processes. Nitrification is the oxidation of ammonia to nitrites then nitrates. Denitrification converts nitrates to N₂ gas. Ammonification is the release of ammonia from organic nitrogen by decomposers. Fixed nitrogen is essential for plant growth.

Explanation:
PCR involves repeated cycles of high-temperature denaturation (around 94°C) to separate the DNA strands. Normal DNA polymerases would be destroyed at these temperatures. Therefore, a thermostable DNA polymerase is required. Taq polymerase, isolated from the thermophilic bacterium Thermus aquaticus found in hot springs, is the most commonly used enzyme because it can withstand the high denaturation temperatures without losing its activity, eliminating the need to add fresh enzyme after each cycle.