Explanation

• Freezing is the process by which a liquid changes to a solid.
• It is the reverse of melting, which is the process by which a solid changes to a liquid.

Last verified on 13-03-2026

Explanation

• Respiration (breathing) is mainly controlled automatically by the brain’s respiratory center in the medulla oblongata.
• Normally, breathing occurs without conscious control, so it is an involuntary process.
• When a person cannot control breathing voluntarily (e.g., during sleep or unconsciousness), the body automatically continues respiration.

Last verified on 13-03-2026

Explanation

• Enamel is the hard, mineralized outer layer of teeth.
• It protects the inner parts of the tooth from damage and decay.
• Enamel is the hardest substance in the human body.
• It is mainly made of calcium phosphate.
  

Additional information:

• Incisors (8) – used for cutting food
• Canines (4) – used for tearing food
• Premolars (8) – help crush and grind food
• Molars (12) – grind food during chewing
• Total adult teeth = 32

Last verified on 13-03-2026

Explanation

• Digestion specifically means the mechanical and chemical breakdown of food into simpler substances.
• Mechanical digestion includes chewing and churning, while chemical digestion involves enzymes and acids.

Additional information:
Main 5 processes of the digestive system:

1. Ingestion – taking food into the body
2. Digestion – mechanical and chemical breakdown of food
3. Absorption – nutrients enter blood through the intestine
4. Assimilation – cells use absorbed nutrients
5. Egestion – removal of undigested waste

Last verified on 13-03-2026

Explanation

• The alimentary canal wall is made of four main tissue layers that help in digestion and movement of food.
• These layers include mucosa, submucosa, muscular layer, and serosa.
• Secretin is not a tissue layer; it is a digestive hormone released by the small intestine.

Last verified on 13-03-2026

Explanation

• The centrosome is a small non-membranous organelle found mainly in animal cells.
• It plays a key role in cell division (mitosis and meiosis) by organizing the spindle fibers.
• It contains two centrioles arranged at right angles.
• The centrosome ensures proper separation of chromosomes during cell division.

Last verified on 13-03-2026

Explanation

• The first compound microscope is believed to have been invented around 1590.
• It was developed by the Dutch spectacle makers Hans Janssen and his son Zacharias Janssen.
• Their invention used two lenses to magnify tiny objects.

Additional information:

• Galileo Galilei – 1609 improved the microscope design
• Robert Hooke – 1665 observed cork cells and wrote Micrographia
• Antonie van Leeuwenhoek – 1674 discovered microorganisms
• Joseph Jackson Lister – 1830 improved modern compound microscope

Last verified on 13-03-2026

Explanation

a:b = 4:9

b:c = 3:5 = 9:15 (multiply by 3)

a:b:c = 4:9:15

Last verified on 13-03-2026

Explanation

Total parts = 6+7+8 = 21

Max share = (8/21) × 105000 = 40000

Last verified on 13-03-2026

Explanation

An arc is a curved portion of the circumference of a circle.

It is formed between two points on the circle’s boundary.

Last verified on 13-03-2026