Explanation: The biosphere is the global sum of all ecosystems — it encompasses every region of Earth where living organisms are found. It includes portions of the lithosphere (land), hydrosphere (water), and atmosphere (air) that support life. The biosphere extends from deep ocean trenches to the lower layers of the atmosphere where microorganisms can survive.

Explanation: The sour taste of a lemon is due to the presence of citric acid. Citric acid is a weak organic acid found naturally in citrus fruits such as lemons, oranges, and limes. It gives them their characteristic tangy flavor and also acts as a natural preservative.

Diseases like Polio and Chicken Pox are caused by viruses. The Polio virus attacks the nervous system and can lead to paralysis, while the Varicella-zoster virus causes Chicken Pox, characterized by itchy blisters and fever. Viruses are acellular infectious agents that can reproduce only inside the living cells of a host organism.

Other options (for context)

• Bacteria: Cause diseases like tuberculosis, cholera, and typhoid, not polio or chicken pox.
• Protozoa: Cause diseases such as malaria and amoebiasis.
• Algae: Generally non-pathogenic; they do not cause human diseases like polio or chicken pox.

Explanation: Adrenaline (also known as epinephrine) is secreted by the adrenal medulla in response to stress, fear, anger, or excitement. It prepares the body for “fight or flight” by increasing heart rate, blood pressure, and glucose levels, and by dilating the air passages to supply more oxygen. Because it helps the body respond instantly to emergencies, it is called the “emergency hormone.”

Explanation: A parity bit is added to binary data in a computer system for error detection. It helps identify whether data has been altered during transmission or storage. The parity bit makes the total number of 1s either even (even parity) or odd (odd parity), allowing simple error checking.