Explanation: The main function of the kidneys is to purify blood by removing waste products, excess salts, and extra water from the body in the form of urine. Each kidney contains about one million nephrons, which are the structural and functional units responsible for blood filtration. The kidneys also help in maintaining the acid-base balance, water balance, and blood pressure, and play a role in hormone secretion such as erythropoietin (for RBC production).

Explanation: The Cerebrum forms about 80% of the total brain mass. It is divided into two hemispheres and is responsible for higher brain functions such as thought, action, reasoning, and emotion. The Cerebellum lies below it and controls coordination and balance, while the Medulla oblongata manages vital involuntary functions.

The aorta is the largest artery in the human body. It originates from the left ventricle of the heart and distributes oxygenated blood to all parts of the body through its various branches. The aorta has thick, elastic walls that can withstand the high pressure of blood pumped directly from the heart. It is divided into parts such as the ascending aorta, aortic arch, and descending aorta.

Other options (for context)

• Capillary: The smallest blood vessels where exchange of gases and nutrients occurs.
• Vena cava: The largest vein, not an artery; it carries deoxygenated blood back to the heart.
• Pulmonary vein: Carries oxygenated blood from the lungs to the heart but is not the largest vessel.

Explanation: Sodium (Na⁺) plays a crucial role in the transmission of nerve impulses in the human body. Nerve cells (neurons) transmit signals through an electrochemical process known as the nerve impulse or action potential. During this process, the movement of sodium (Na⁺) and potassium (K⁺) ions across the nerve cell membrane generates an electrical charge. The rapid influx of sodium ions causes depolarization, which allows the nerve impulse to travel along the neuron, ensuring proper communication between the brain, spinal cord, and body.

Explanation: The femur is the single bone of the thigh region and extends from the hip joint to the knee joint. It supports the body’s weight during standing, walking, and running. The femur is the longest, heaviest, and strongest bone in the human skeleton. It articulates with the pelvic girdle at its proximal end (head of femur fits into the acetabulum of the pelvis) and with the tibia and patella at the distal end.

Average Length: Approximately 45 cm (about 1/4 of body height).

Explanation: Mucor is not a biofertilizer; it is a saprophytic fungus that grows on decaying organic matter. Biofertilizers are living microorganisms that enhance soil fertility by fixing atmospheric nitrogen or solubilizing nutrients. Examples include Rhizobium, Azotobacter, and Anabaena.

Nickel exposure commonly causes a skin disease called Dermatitis, specifically Allergic Contact Dermatitis. This condition occurs when the skin comes into direct contact with nickel-containing objects such as jewelry, coins, or belt buckles. It leads to redness, itching, and rashes, especially in sensitive individuals. Nickel allergy is one of the most common metal allergies worldwide.

Other options (for context)

• Itai Itai: Caused by cadmium poisoning, not nickel.
• Learning Disability: Not directly linked to nickel exposure.
• Asthma: May be aggravated by pollutants, but not typically caused by nickel.

Explanation: A sphygmomanometer is a medical instrument used to measure blood pressure. It consists of an inflatable cuff, a mercury or aneroid gauge, and a bulb for inflation. The cuff is wrapped around the upper arm and inflated to temporarily stop blood flow. As pressure is slowly released, readings are taken for systolic (maximum) and diastolic (minimum) pressure. Normal blood pressure for a healthy adult is about 120/80 mmHg.

Explanation: The intensity and magnitude of an earthquake are measured using a scientific instrument called a seismograph. It records the vibrations or seismic waves produced by earthquakes. The data obtained from a seismograph are used to calculate the earthquake’s strength on scales such as the Richter Scale or the Moment Magnitude Scale. The seismogram (the recorded graph) shows the amplitude and duration of the waves, helping scientists locate the earthquake’s epicenter and determine its severity.