Explanation: Dehydration happens when the body loses excessive water through sweating, vomiting, diarrhea, or inadequate fluid intake. It disturbs the balance of electrolytes and reduces blood volume, leading to symptoms such as thirst, dry mouth, fatigue, and dizziness. To prevent dehydration, oral rehydration solutions (ORS) or adequate water intake are essential.

Explanation: The erythrocytes (RBCs) play a crucial role in the circulation of blood by carrying oxygen from the lungs to body tissues and returning carbon dioxide for exhalation. They contain hemoglobin, which binds oxygen and maintains the red color of blood. Circulation itself is driven by the heart and supported by these oxygen-carrying cells.

Explanation: Sodium hydroxide (NaOH) is a base, so it does not turn blue litmus paper red. Instead, it turns red litmus paper blue. In contrast, lemon juice, acetic acid, and hydrochloric acid are acidic and turn blue litmus red.

Explanation: Every computer connected to the Internet is identified by a unique numerical label called an IP Address (Internet Protocol Address). It consists of four numeric parts separated by dots (e.g., 192.168.1.1) and is used to locate and communicate with devices over the network.

Explanation: Alcohols are organic compounds composed of carbon (C), hydrogen (H), and oxygen (O). They are characterized by the presence of one or more hydroxyl (-OH) functional groups attached to a carbon atom. The general formula of alcohols is C_nH_2n+1OH. A common example is ethanol (C₂H₅OH), which is used in beverages, fuels, and sanitizers. The -OH group makes alcohols polar, soluble in water (especially lower alcohols), and reactive in many organic reactions.

Running water is the source of hydel power (also called hydroelectric power). The energy of flowing or falling water is converted into electrical energy using turbines and generators in dams. It is a renewable, clean, and sustainable source of energy widely used in India and worldwide.

• Thermal power: Generated by burning coal or other fuels.
• Nuclear power: Produced from nuclear fission reactions.
• None of the above: Incorrect — running water directly produces hydel power.

Explanation: A CD-ROM (Compact Disc Read-Only Memory) is an optical disk used to store large amounts of data. It is read using a laser beam in a CD drive and is commonly used for distributing software, music, and multimedia content.

Explanation: Vitamins are classified into two categories based on their solubility — fat-soluble and water-soluble. Vitamin C (ascorbic acid) and the B-complex vitamins are water-soluble, meaning they dissolve in water and are not stored in the body. Therefore, they must be consumed regularly through diet. Deficiency of Vitamin C causes scurvy, characterized by bleeding gums and delayed wound healing.