Explanation

• Mac OS is the operating system developed by Apple Inc. for its Mac computers.
• First introduced in 1984 with the original Macintosh.
• Known for its user-friendly interface, stability, and security features.

Additional information:

• Android → Developed by Google
• Windows → Developed by Microsoft

Last verified on 09-02-2026

Explanation

• GDP (Gross Domestic Product) measures the total monetary value of all goods and services produced within a country in a specific time period, usually one year.

Additional information:

Components of GDP:

• Consumption (household spending)
• Investment (business spending)
• Government spending
• Net exports (exports − imports)

Last verified on 09-02-2026

Explanation

• Man-made disasters are caused by human activities rather than natural events.
• Industrial accidents (e.g., chemical spills, factory explosions) are directly caused by humans.

Additional information:

Examples of industrial accidents:

• Bhopal gas tragedy, 1984
• Chernobyl nuclear disaster, 1986

Last verified on 09-02-2026

Explanation

• The name Muhammad (PBUH) means “the praised one” in Arabic.
• It reflects the honor and respect associated with the Prophet Muhammad (PBUH).
• The name Ahmed (PBUH) means "highly praised".

Last verified on 09-02-2026

Explanation

• Birds have hollow (pneumatic) bones to make their skeleton lighter, aiding flight efficiency.
• Hollow bones reduce overall body weight without sacrificing strength.
• This adaptation is crucial for sustained flying and gliding.

Last verified on 09-02-2026

Explanation

• The ozone layer absorbs and blocks the majority of the Sun’s harmful ultraviolet (UV) radiation.
• This protection helps prevent skin cancer, cataracts, and damage to ecosystems.

Last verified on 09-02-2026

Explanation

• Data collection and analysis rely on accurate observations and measurements.
• If proper observations are not made, the experiment’s results will be unreliable.
• Other steps like hypothesis generation or reasoning depend on this data for validation.

Last verified on 09-02-2026

Explanation

• Endothermic reactions absorb heat from the surroundings (e.g., photosynthesis, melting ice).
• Exothermic reactions release heat to the surroundings (e.g., burning fuel, respiration).
• The key difference is heat flow direction between the system and environment.

Additional information:

• Endothermic → feels cold to touch
• Exothermic → feels hot to touch
• Examples help remember: Ice melting (endo), Fire burning (exo)

Last verified on 09-02-2026

Explanation

• Endothermic reactions absorb heat from the surroundings.

Examples:

• Photosynthesis → plants absorb sunlight to make glucose
• Melting of ice → absorbs heat to change solid → liquid
• Dissolving ammonium nitrate in water → absorbs heat, feels cold

Burning of fuel is exothermic, releasing heat and light.

Last verified on 09-02-2026

Explanation

• Chemical changes produce new substances with different properties.

Examples:

• Cooking of food → new substances formed
• Burning of paper → produces ash and gases
• Rusting of iron → iron reacts with oxygen to form rust

Melting of ice is a physical change, only changing state from solid to liquid, no new substance is formed.

Last verified on 09-02-2026