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: Mars is known as the Red Planet because its surface contains a large amount of iron oxide (rust), which gives it a reddish appearance. It is the fourth planet from the Sun and has two moons — Phobos and Deimos.

Explanation: Cow’s milk is a nutritionally rich food containing proteins, fats, carbohydrates, minerals, and vitamins. It is particularly rich in B-group vitamins, especially Vitamin B₂ (Riboflavin) and Vitamin B₁₂ (Cobalamin). These vitamins play crucial roles in maintaining healthy skin, eyesight, and the nervous system, as well as aiding in the formation of red blood cells.

Note: While milk provides moderate amounts of Vitamin A and D, the natural content of Vitamin D is low, and milk is often fortified with Vitamin D to enhance its nutritional value.

Explanation: The star rating system seen on electrical appliances (like ACs, refrigerators, and fans) represents the energy efficiency of the product. It is issued by the Bureau of Energy Efficiency (BEE), under the Ministry of Power, Government of India. The more the number of stars (up to 5), the higher the energy efficiency — meaning the appliance consumes less electricity for the same performance. However, the star rating does not indicate the lifespan or the quality checks of the appliance.

The average distance between the Earth and the Sun is approximately 150 million kilometers (or about 1 Astronomical Unit – 1 AU). This distance serves as a standard unit of measurement for describing distances within our solar system. Despite slight variations due to Earth's elliptical orbit, this average remains nearly constant and is crucial for maintaining suitable conditions for life on Earth.

Other options (for context)

• 15 Million km: Far too close — the Earth would be extremely hot and uninhabitable.
• 90 Million km: Shorter than the actual average distance.
• 900 Million km: Much greater — about six times the real distance, closer to Saturn’s orbit.

Explanation: Malaria is caused by a parasitic infection of the genus Plasmodium. The disease spreads to humans through the bite of an infected female Anopheles mosquito. When the mosquito bites, it injects Plasmodium sporozoites into the bloodstream, which travel to the liver, multiply, and infect red blood cells. Common species causing malaria include P. vivax, P. falciparum, P. malariae, and P. ovale. Symptoms include fever, chills, sweating, and anemia. It can be prevented by mosquito control and use of antimalarial drugs.

Explanation: According to the Bureau of Indian Standards (BIS) – IS 10500:2012, the acceptable limit of total hardness in drinking water, expressed as CaCO₃, is 200 mg/l. The permissible limit in the absence of an alternate source is up to 600 mg/l. Excess hardness can cause scaling and affect the taste of water.