Explanation: Haemoglobin is a complex iron-containing protein found in red blood cells (RBCs). It binds with oxygen in the lungs to form oxyhaemoglobin and releases it in tissues where oxygen levels are low. It also helps transport carbon dioxide from tissues back to the lungs. This oxygen-carrying property makes haemoglobin the essential respiratory pigment in humans and most vertebrates.

Sound becomes hazardous and causes noise pollution when its intensity exceeds 80 decibels (dB). Prolonged exposure to such high noise levels can lead to hearing loss, stress, sleep disturbances, and other health problems. Common sources include heavy traffic, loudspeakers, machinery, and construction activities. Sounds above 120 dB can cause immediate ear damage or pain.

Other options (for context)

• Above 50 dB: Considered moderate — typical of normal conversation or office noise.
• Above 100 dB: Very loud and potentially painful, but 80 dB is the threshold for long-term hazard.
• Above 130 dB: Extremely loud, causes immediate physical pain and ear damage.

Explanation: Entomology is a branch of Zoology that focuses on the study of insects, including their structure, classification, behavior, ecology, and evolution. Insects make up more than 75% of all known animal species on Earth and play crucial roles in pollination, decomposition, and food chains. Scientists who study insects are known as entomologists.

Explanation: Plants absorb nitrogen from the soil mainly in the form of nitrates (NO₃⁻). Inside the plant, nitrates are reduced to nitrites (NO₂⁻) and then to ammonia (NH₃) through the action of specific reductase enzymes. The ammonia thus formed is then used to synthesize amino acids, proteins, nucleic acids, and other nitrogen-containing compounds necessary for plant growth.

Simplified Pathway:

NO₃⁻ → NO₂⁻ → NH₃ → Amino acids → Proteins

Explanation: Cobalt-60 (Co-60) is a radioactive isotope of cobalt that emits high-energy gamma rays during its decay process. It decays into Nickel-60 (Ni-60) by beta decay, releasing two strong gamma photons of energies 1.17 MeV and 1.33 MeV. Due to these intense gamma emissions, Co-60 is widely used in radiation therapy (teletherapy) for cancer treatment, as well as in industrial radiography and sterilization of medical equipment. Gamma rays have high penetration power, allowing them to destroy cancerous cells deep inside tissues.

Explanation: The pale yellow color of normal human urine is due to the presence of a pigment called Urochrome. It is produced from the breakdown of hemoglobin in red blood cells. The intensity of the color depends on the concentration of the urine — darker yellow indicates concentrated urine, while very pale or colorless urine suggests dilution due to high water intake.

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.

Explanation: Vitamin A is essential for maintaining healthy vision, skin, and immune function. A deficiency of Vitamin A leads to night blindness (nyctalopia), a condition in which a person has difficulty seeing in dim light or at night. In severe cases, it can cause xerophthalmia (dryness of the cornea) and even blindness. Vitamin A is obtained from foods such as carrots, milk, butter, fish liver oil, and green leafy vegetables.