Assertion (A): The color of urine is due to urobilin. Reason (R): Urobilin is a breakdown product of hemoglobin. MCQ with Answer and Explanation

Explanation:
The femur (thigh bone) is the longest, strongest, and heaviest bone, supporting body weight during standing and walking.

Explanation:
Veins have thinner walls and larger lumens; arteries are thick and elastic; capillaries are thin for exchange; venules are larger than capillaries. Valves are in veins.

Explanation:
Coal is a fossil fuel formed over millions of years and is finite, thus non-renewable. Solar, wind, and tidal energy are renewable and replenishable. Non-renewable resources include coal, petroleum, natural gas, and nuclear minerals. Overexploitation leads to depletion and environmental pollution. Conservation of such resources is essential for sustainable development.