Which of the following is a water-soluble vitamin? MCQ with Answer and Explanation

Explanation:
Diamond has a three-dimensional network of strong covalent bonds between carbon atoms (sp³ hybridization). This giant covalent structure gives diamond its extreme hardness, high melting point, and electrical insulating property. Graphite also has covalent bonds within layers but conducts due to delocalized electrons. Ionic bonds are in NaCl, metallic bonds in metals, hydrogen bonds in water.

Explanation:
Polythene (polyethylene) softens on heating and can be remolded, thus thermoplastic. Bakelite and melamine are thermosetting (cannot be remolded). Vulcanized rubber is also thermoset due to cross-linking. Thermoplastics have linear or branched chains, no cross-links.

Explanation:
NPK stands for Nitrogen (N), Phosphorus (P, as P₂O₅), and Potassium (K, as K₂O). These are primary macronutrients essential for plant growth. The numbers on a fertiliser bag (e.g., 10-26-26) indicate the percentage of N, P₂O₅, and K₂O.