All Free Everyday Science MCQs with Answers

821. How many layers of Atmosphere?

• A. 2
• B. 3
• C. 4
• D. 5

Explanation: The atmosphere is conventionally divided into five layers: troposphere, stratosphere, mesosphere, thermosphere and exosphere. Some classifications combine layers or add subdivisions, but five is the standard school-level answer.

822. A body of land that is surrounded by water on three sides is called________?

• A. Strait
• B. Bay
• C. Peninsula
• D. Gulf

Explanation: A peninsula is a landform almost surrounded by water but connected to a larger landmass on one side. A strait is a narrow water passage, while a bay and gulf are bodies of water partly enclosed by land.

823. The study of fish is known as ________?

• A. Entomology
• B. Ichthyology
• C. Ecology
• D. None of these

Explanation: Ichthyology is the branch of zoology concerned with fish, including their classification, behaviour and biology. Entomology instead deals with insects.

824. The scientific study of insects is known as _______?

• A. Ichthyology
• B. Entomology
• C. Zoology
• D. Botany

Explanation: Entomology is the scientific study of insects. Ichthyology studies fish, whereas botany studies plants.

825. The study of organisms and their environment is known as ________?

• A. Acoustics
• B. Ecology
• C. Ichthyology
• D. None of these

Explanation: Ecology examines relationships between organisms and their physical surroundings, including food chains and habitats. Acoustics is the study of sound.

826. The main culprit of greenhouse effect is Carbon dioxide. But which is the second element contributing most to greenhouse effect

• A. Nitrogen Dioxide (NO2)
• B. Chlorofluorocarbons (CFCs)
• C. Methane (CH4)
• D. High-fructose corn syrup (HFCs)

Explanation: Among the listed gases, methane is generally identified as the second-largest contributor to human-caused greenhouse warming after carbon dioxide. CFCs are extremely powerful per molecule but occur in much smaller amounts.

827. As a result of which treaty, ozone hole in Antarctica is slowly healing?

• A. Koyoto protocol
• B. Ottawa treaty
• C. Montreal protocol
• D. Oslo Accord

Explanation: The Montreal Protocol controls ozone-depleting chemicals such as CFCs, allowing stratospheric ozone to recover gradually. The Kyoto Protocol mainly addressed greenhouse-gas emissions.

828. Montreal Protocol 1987 was__________?

• A. Treaty among nations to reduce nuclear arsenals
• B. Climate control treaty
• C. Treaty to protect ozone layer
• D. Trade policy about tarrifs

Explanation: The 1987 Montreal Protocol is an international agreement to phase out substances that destroy the ozone layer, especially CFCs. It is not a nuclear-arms or tariff treaty.

829. Disolved oxygen (DO) in water should be?

• A. 400 to 800 ppm
• B. 4000 to 8000 ppm
• C. 0.4 to 0.5 ppm
• D. 4 to 5 ppm

Explanation: Dissolved oxygen in reasonably healthy water is commonly around 4 to 5 ppm or higher, with cold, clean water holding more oxygen. The hundreds or thousands of ppm options are far too high for ordinary water.

830. Why normal rain is slightly acidic?

• A. due to presence of dust in air
• B. carbon dioxide and water in clouds react to form carbonic acid
• C. Ozone depletion
• D. All of these

Explanation: Rain absorbs atmospheric carbon dioxide, forming weak carbonic acid and giving normal rain a mildly acidic pH. Ozone depletion and dust are not the basic chemical cause of ordinary rain's acidity.