Explanation

Blank DVDs that allow data to be erased and rewritten multiple times are called DVD+RW.

Standard DVDs can only be written once and cannot be reused.

Rewritable DVDs are useful for backups, software, and data transfer.

Additional information:

• DVD+RW can be rewritten up to 1000 times.
• Standard DVD (DVD-R or DVD+R) can only be written once.
• Rewritable DVDs are commonly used for temporary data storage and software testing.

Last verified on 16-01-2026

Explanation

Aluminum is a metal that can be recycled many times without losing its properties.

Additional information:

• Recycling 1 ton of aluminum saves up to 95% of the energy required to make new aluminum.
• Aluminum is widely used in cans, foils, and packaging, making it highly recyclable.

Last verified on 16-01-2026

Explanation

• Location: Amazon Rainforest, South America
• Area Affected: ~17% of forest lost in last 50 years
• Causes: Agriculture, cattle ranching, logging, urbanization
• Impact: Loss of biodiversity, carbon emissions, climate change

Additional information:

• Amazon forest is called the “lungs of the Earth”

Last verified on 16-01-2026

Explanation

• Main Cause: Freon / CFCs
• Effect: Breaks down O₃ molecules → more UV-B radiation
• Other Contributors: Halons, carbon tetrachloride
• Result: Skin cancer, cataracts, climate impact

• The Montreal Protocol (1987) aimed to reduce CFC emissions
• Ozone layer protects Earth from harmful ultraviolet rays

Explanation

Fossils are mainly found in sedimentary rocks.

Additional information:

• Rock Type: Sedimentary rocks (e.g., sandstone, limestone, shale)
• Formation: Layered deposition of sediments over time
• Contains: Fossils of plants, animals, and microorganisms
• Not in: Igneous or metamorphic rocks usually

Last verified on 16-01-2026

Explanation

Coniferous forests (taiga) have lower biodiversity compared to tropical rain forests.

Additional information:

• Coniferous Forests: Taiga, found in northern regions, dominated by conifers (pine, spruce)
• Biodiversity: Lower due to cold climate, acidic soil, and short growing season
• Tropical Rainforests: High biodiversity, thousands of plant and animal species
• Examples: Amazon, Congo, Southeast Asia

Last verified on 16-01-2026

Explanation

• Vitamin Name: B12 (Cobalamin)
• Source: Produced by gut bacteria; present in meat, fish, eggs, dairy
• Function: Essential for RBC formation, nerve function, DNA synthesis
• Not Found In: Fruits and vegetables

Last verified on 16-01-2026

Explanation

Pasteurization of milk is a heat treatment process used to kill harmful microorganisms.

In the HTST method, milk is heated to 161°F (72°C) for 15 seconds.

Additional information:

• Another method: LTLT → 145°F for 30 minutes
• Pasteurization improves safety and shelf life of milk

Last verified on 16-01-2026

Explanation

Fats and oils provide more energy than carbohydrates and proteins. 

• Energy from fats: ~9 kcal/g
• Energy from carbs: ~4 kcal/g
• Energy from proteins: ~4 kcal/g
• Ratio: 9 ÷ 4 = 2.25 times

Last verified on 16-01-2026

Explanation

Vitamin C (Ascorbic acid) helps prevent browning in fruits.

By inhibiting the enzymes responsible for oxidation.

It is commonly used to keep cut fruits fresh.

Additional information:

• Commonly used in food preservation (lemon juice on fruits)
• Also essential for immunity and collagen formation

Last verified on 16-01-2026