Karakoram Highway length is about 1600 km connecting Pakistan and China.

Sunspots are dark regions that appear on the surface of the Sun due to intense magnetic activity that lowers the surface temperature in those areas. The first recorded telescopic observation of sunspots is credited to Thomas Harriot, an English astronomer, in 1610. He used an early telescope to observe the Sun and documented these spots before Galileo’s more widely known observations. This discovery challenged the long-standing Aristotelian belief that celestial bodies were perfect and unchanging. The presence of spots on the Sun suggested that it was dynamic and imperfect. Later astronomers such as Galileo Galilei and Christoph Scheiner studied sunspots more extensively and tracked their movement, which helped establish that the Sun rotates on its axis. Albert Einstein is known for the theory of relativity, Isaac Newton for gravity and laws of motion, and René Descartes for contributions to philosophy and mathematics. None of them observed sunspots first. Thus, Thomas Harriot is considered the earliest observer, making option D correct. His work contributed significantly to the development of modern astronomy and our understanding of solar activity.

The human brain is composed of approximately 75% water, making it one of the most water-rich organs in the body. Water is essential for maintaining brain function, including nutrient transport, temperature regulation, and electrical activity. Adequate hydration is crucial for cognitive functions such as memory, concentration, and alertness. Even mild dehydration can impair brain performance. The other percentages are either too low or too high to accurately represent the brain’s composition. Thus, 75% is the correct answer. This emphasizes the importance of water in maintaining overall health and brain function.

Mastication refers to the process of chewing food in the mouth. It is the first step of digestion, where food is broken down into smaller pieces by the teeth and mixed with saliva. Saliva contains enzymes such as amylase, which begin the chemical digestion of carbohydrates. Chewing also increases the surface area of food, making it easier for digestive enzymes to act. Assimilation refers to the use of absorbed nutrients by the body, absorption is the uptake of nutrients into the bloodstream, and excretion is the removal of waste. Thus, chewing of food is the correct answer. Mastication is essential for proper digestion and nutrient absorption. Understanding digestive processes is important in biology and health sciences.

The Paris Climate Conference (COP21) was held in 2015, leading to the Paris Agreement aimed at limiting global warming below 2°C.