Explanation: Dengue fever is caused by the Dengue virus, which belongs to the Flavivirus group. It is transmitted to humans through the bite of an infected Aedes aegypti mosquito. The virus multiplies in the blood and causes symptoms such as high fever, severe headache, joint and muscle pain, rashes, and low platelet count. In severe cases, it can lead to Dengue hemorrhagic fever or Dengue shock syndrome. Prevention includes controlling mosquito breeding and avoiding mosquito bites.

Explanation: Fire extinguishers commonly used in houses and offices contain water, potassium bicarbonate (KHCO₃), and fluorocarbons. These chemicals help in extinguishing fires by cooling, cutting off oxygen supply, and preventing the spread of flames without leaving harmful residues.

Explanation: Among the given particles, the proton is the heaviest. A proton is a positively charged subatomic particle found in the nucleus of an atom, with a mass of approximately 1.672 × 10⁻²⁷ kg. Although the neutron is slightly heavier than a proton, in most general questions like this one, protons are considered heavier in context when compared with electrons and neutrinos. Electrons are much lighter, with a mass about 1/1836 that of a proton, while neutrinos are nearly massless and electrically neutral.

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.

The Kyoto Protocol is an international agreement related to the environment, specifically aimed at reducing greenhouse gas emissions that contribute to global warming and climate change. It was adopted in Kyoto, Japan, in 1997 and came into force in 2005. The protocol set binding targets for developed countries to limit or reduce their carbon dioxide (CO₂) and other greenhouse gas emissions.

Other options (for context)

• Nuclear Power: Not the focus of the Kyoto Protocol; this relates to energy generation and atomic energy regulation.
• Trade: Covered under agreements like GATT and WTO, not the Kyoto Protocol.
• None of these: Incorrect — the Kyoto Protocol deals specifically with environmental protection.

Explanation: Seismology is the branch of geophysics that deals with the study of earthquakes and the propagation of seismic waves through the Earth. Scientists who study earthquakes are called seismologists. Seismology helps in understanding the origin, intensity, and effects of earthquakes, as well as the internal structure of the Earth. The intensity of an earthquake is measured using instruments like the seismograph and scales such as the Richter scale or Moment Magnitude scale.

Velocity is a vector quantity because it has both magnitude and direction. It represents the rate of change of displacement of an object. Unlike speed, which only tells how fast an object is moving, velocity also indicates the direction of motion.

Other options (for context)

• Mass: A scalar quantity — it has magnitude only, no direction.
• Volume: Scalar — represents space occupied by matter, without direction.
• Speed: Scalar — measures how fast an object moves but not in which direction.

Explanation: Albert Einstein received the Nobel Prize in Physics in 1921 for his discovery of the photoelectric effect, not for his famous theory of relativity. In the photoelectric effect, when light of a certain frequency falls on a metal surface, it emits electrons. Einstein explained this phenomenon by proposing that light is made up of discrete packets of energy called photons. The energy of each photon is given by E = hν, where h is Planck’s constant and ν is the frequency of light. This discovery laid the foundation for quantum physics and modern electronics.