Which of the following structures prevents the entry of food into the trachea during swallowing? MCQ with Answer and Explanation

Explanation:
Niacin is part of NAD⁺/NADH, which donates electrons to the electron transport chain to generate the proton gradient for ATP synthesis. All B vitamins contribute indirectly.

Explanation:
Prokaryotic cells (bacteria, archaea) are characterized by the absence of a true, membrane-bound nucleus; their genetic material is located in a nucleoid region. Eukaryotic cells (plants, animals, fungi, protists) possess a true nucleus and various membrane-bound organelles like mitochondria, ER, and Golgi. Plant cells are distinguished from animal cells by the presence of a rigid cell wall made primarily of cellulose, along with chloroplasts and a large central vacuole. Thus, statements 1 and 2 are correct.

Explanation:
A food chain shows the flow of energy from producer to consumers. Grass (producer) → Grasshopper (primary consumer/herbivore) → Frog (secondary consumer/carnivore) → Snake (tertiary consumer). Arrows point in the direction of energy flow. Option A has incorrect order, C and D start with consumer. Typically, energy decreases at each trophic level. This illustrates the correct trophic sequence.