Rainfall is measured using a rain gauge, a meteorological instrument designed to collect and measure precipitation. It typically consists of a funnel that directs rainwater into a measuring cylinder. The amount of rainfall is recorded in millimeters, representing the depth of water that would accumulate on a flat surface. Accurate rainfall data is essential for agriculture, flood prediction, and weather forecasting. A hydrometer measures liquid density, not rainfall. “Rain meter” and “hydroscope” are not standard instruments. Thus, rain gauge is the correct answer. It is widely used by meteorological departments worldwide.

Qadirpur Gas Field, located in Sindh, is the second largest gas field operated by Oil and Gas Development Company Limited (OGDCL) in Pakistan. It was discovered in 1989 and plays a major role in supplying natural gas for domestic and industrial use. The largest gas field in Pakistan is Sui, located in Balochistan, which makes it incorrect for this question. Qadirpur follows as the second largest and contributes significantly to energy production. The gas extracted from Qadirpur is used for electricity generation, fertilizer production, and household consumption. Its development has helped strengthen Pakistan’s energy security. Kohat and Gwadar are not major gas fields under OGDCL. Therefore, Qadirpur is the correct answer. Understanding such fields is important for exams and also provides insight into Pakistan’s energy resources and economic development.

The 1935 earthquake struck Quetta, now the capital of Balochistan, Pakistan. It occurred on May 31, 1935, with an estimated magnitude of around 7.7, making it one of the most destructive earthquakes in the region’s history. The earthquake caused massive destruction because most buildings were made of mud and were not designed to withstand seismic activity. It is estimated that between 30,000 and 60,000 people lost their lives. The disaster occurred early in the morning, which increased casualties as people were indoors. Quetta lies in a seismically active zone due to the collision of the Indian and Eurasian tectonic plates. This makes the region highly prone to earthquakes. The 1935 event highlighted the need for earthquake-resistant construction and better disaster preparedness. Other cities like Karachi, Lahore, and Jhelum have not experienced such catastrophic earthquakes historically. Therefore, Quetta is the correct answer. This event remains a key example in studies of seismic hazards and urban vulnerability in South Asia.

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.

Benjamin Franklin, a prominent American scientist and statesman, invented both the lightning rod and bifocal spectacles. His lightning rod invention emerged from his experiments with electricity, including the famous kite experiment, which demonstrated that lightning is a form of electrical discharge. The lightning rod protects buildings by directing electrical energy safely into the ground, preventing fires and structural damage. This invention had immediate practical importance and is still widely used today. Franklin also invented bifocal spectacles to address his own vision problems. These glasses combine two lenses in one frame, allowing a person to see both near and distant objects clearly without switching glasses. This was a major convenience and innovation in optics. Other options are notable scientists but unrelated to both inventions: Thomas Edison developed electric devices, Alessandro Volta invented the battery, and Benjamin Banneker was a mathematician and astronomer. Therefore, Benjamin Franklin is the correct answer, as he contributed significantly to both electrical science and practical inventions improving daily life.