Explanation: Minamata disease was caused by severe mercury poisoning in the coastal city of Minamata, Japan. It resulted from the discharge of methyl mercury compounds into Minamata Bay by a chemical factory (Chisso Corporation) during the 1950s and 1960s. The toxic mercury accumulated in fish and shellfish, which were later consumed by local residents. Symptoms included numbness, muscle weakness, loss of vision, hearing and speech, paralysis, and in severe cases, death. This incident is one of the world’s worst cases of industrial pollution.

Explanation: Acid rain is caused by the presence of pollutant gases such as sulphur dioxide (SO₂) and nitrogen oxides (NOₓ) in the atmosphere. These gases are released mainly from burning of coal, oil, and industrial emissions. When they combine with water vapor in the atmosphere, they form sulphuric acid (H₂SO₄) and nitric acid (HNO₃), which fall to the ground as acid rain. It damages soil, plants, aquatic life, and even buildings and monuments made of marble or limestone.

Sputnik I was the first artificial satellite to orbit the Earth. It was launched by the Soviet Union on October 4, 1957. The successful launch of Sputnik I marked the beginning of the space age and initiated the space race between the USA and the USSR.

• Explorer I: First U.S. satellite, launched in 1958.
• Vanguard I: A U.S. satellite launched later in 1958.
• Discoverer I: Part of an American reconnaissance satellite program (1959).

Explanation: A barometer is an instrument used primarily for measuring atmospheric pressure. It helps in weather forecasting and determining altitudes (since atmospheric pressure decreases with height). A mercury barometer consists of a glass tube filled with mercury inverted in a mercury reservoir. When air pressure changes, the height of the mercury column changes accordingly. However, a barometer cannot measure the density of a liquid — that function is performed by a hydrometer.

Explanation: Uranium-235 (U-235) is the isotope used for the production of atomic energy because it is fissionable. When bombarded with neutrons, U-235 undergoes nuclear fission, releasing a large amount of energy along with additional neutrons, which sustain the chain reaction in nuclear reactors and atomic bombs.

Explanation: Marijuana is a psychoactive drug obtained from the female inflorescence (flowering tops) of the Cannabis sativa plant. It contains the active compound tetrahydrocannabinol (THC), which affects the central nervous system and alters mood and perception.