Explanation: The thyroid gland is located in the neck region, just below the larynx (voice box) and in front of the trachea (windpipe). It is a butterfly-shaped endocrine gland that secretes the hormones thyroxine (T₄) and triiodothyronine (T₃). These hormones regulate metabolism, growth, and energy production in the body. The thyroid also produces calcitonin, which helps control calcium levels in the blood. Iodine is essential for the synthesis of thyroid hormones.

Explanation: Respiration is a biochemical process in which food molecules (mainly glucose) are oxidized to release energy in the form of ATP (adenosine triphosphate). This energy is then used for various life processes such as movement, growth, repair, and maintenance. Respiration occurs in all living cells and takes place mainly inside the mitochondria.

Chemical Equation:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)

In contrast, photosynthesis stores energy in glucose molecules, while respiration releases that stored energy for cellular use.

Explanation: The speed of internet connectivity is expressed in Megabits per second (Mb/sec or Mbps). It indicates how much data is transferred per second over a network connection. One megabit equals 1,000,000 bits. Higher Mbps values mean faster internet speeds. For example, a 100 Mbps connection can transfer 100 million bits of data every second. Note that 1 byte = 8 bits, so internet speeds in Mbps differ from file sizes, which are usually measured in megabytes (MB).

Explanation: The full form of OMR is Optical Mark Recognition. It is a technology used to detect marks made on specially designed paper forms, such as answer sheets in competitive exams or surveys. Candidates mark their answers by filling bubbles with dark ink or pencil, and the OMR scanner reads these marks by detecting reflected light. This process allows for fast, accurate, and automated data collection without manual checking, minimizing human errors and saving time.

Explanation: The Sun is seen a few minutes before actual sunrise and after actual sunset due to the refraction of light by the Earth's atmosphere. The atmosphere bends the Sun’s rays towards the Earth, making the Sun appear slightly above the horizon even when it is below it.

Explanation: AIDS, Hepatitis, and Typhoid fever are all diseases that can be spread by human beings. While AIDS and Hepatitis are viral diseases and Typhoid is a bacterial disease, all three are transmitted through contact with infected individuals or their body fluids, making human-to-human transmission common.

The normal hearing range of human beings is from 20 Hz to 20,000 Hz (20 kHz). Sounds below 20 Hz are called infrasonic sounds, while those above 20,000 Hz are known as ultrasonic sounds, both of which are inaudible to humans. With age or prolonged exposure to loud noise, the upper hearing limit tends to decrease, reducing sensitivity to high-frequency sounds.

Other options (for context)

• 30 to 30,000 Hz: Incorrect — exceeds the upper audible limit for humans.
• 50 to 50,000 Hz: Incorrect — animals like dogs and bats can hear this range, not humans.
• 40 to 40,000 Hz: Incorrect — the human ear cannot detect frequencies that high.

Aryabhatta was a renowned mathematician and astronomer of ancient India. He lived during the Gupta period (around 476–550 CE) and authored the famous work Aryabhatiya. Aryabhatta introduced the concept of zero (0) and explained the place value system. He also proposed that the Earth rotates on its axis and correctly explained solar and lunar eclipses.

Other options (for context)

• Doctor: No historical evidence of Aryabhatta being a physician.
• Poet: Although his works were written in verse form, his main field was mathematics and astronomy.
• Physicist: The term did not exist in his time; however, his scientific thinking laid foundations for later studies.