Explanation

• Washing soda is also known as sodium carbonate (Na2CO3).
• It is used to remove permanent hardness of water.
• Permanent hardness is caused by the presence of magnesium and calcium sulfates or chlorides in water, which cannot be removed by boiling.
• Washing soda helps to precipitate these minerals, making the water softer.

Last verified on 23-04-2026

Explanation

• Sugar is the most soluble chemical in water.
• Sugar is made from sucrose.
• Sugar dissolves readily in water due to its polar nature.
• It forms hydrogen bonds with water molecules, increasing solubility.
• Used widely in food and beverages due to easy dissolution.

Last verified on 23-04-2026

Explanation

• The longest cell in the human body is the nerve cell (neuron).
• Some neurons can extend up to 1 meter in length.
• They transmit impulses throughout the body.

Additional information:

• The smallest cell in the human body is the sperm cell (spermatozoon).
• It is measures approximately 4–5 micrometers (µm) in length.
• It is mainly consisting of a nucleus and a tail.

Last verified on 23-04-2026

Explanation

• Allergy is an abnormal immune response to harmless substances like dust or pollen.
• It occurs when the body reacts excessively to an allergen.
• This reaction involves the immune system producing antibodies.
• Thus, allergy is mainly due to an antigen–antibody reaction.

Last verified on 23-04-2026

Explanation

• A reflex action is a quick, automatic response to a stimulus.
• It is mainly controlled by the spinal cord, which is part of the central nervous system.
• This allows fast response without involving the brain immediately.
• Thus, reflexes are coordinated by the central nervous system.

Last verified on 23-04-2026

Explanation

• The kidney is an important organ responsible for filtering blood and forming urine.
• Its structural and functional unit is the nephron.
• Each kidney contains millions of nephrons.
• They perform filtration, reabsorption, and secretion.

Last verified on 23-04-2026

Explanation

• National Product (GDP) measures the value of final goods and services produced in an economy.
• The sale of a new car by a dealer is already included in production when the car is manufactured.
• Dealer’s sale is only a distribution/transfer within the production chain, not new production.
• Therefore, it does not add to national product again.

Last verified on 23-04-2026

Explanation

• Protectionism in international trade refers to government policies that restrict free trade.
• It includes tariffs, quotas, and other barriers to protect domestic industries.
• Trade is not fully free nor fully closed, but restricted to some extent.
• Therefore, it is often described as semi-restricted trade.

Last verified on 23-04-2026

Explanation

• An indifference curve shows combinations of two goods that give equal satisfaction.
• Normally, it is downward sloping and convex to the origin due to diminishing MRS.
• A horizontal indifference curve would mean utility changes only with one good, which is unrealistic in standard theory.
• Therefore, it does not represent a valid standard case in consumer theory.

Last verified on 23-04-2026

Explanation

• Transfer payments are payments made without receiving any goods or services in return.
• Old age pension is given by the government to support elderly people.
• It is not related to current production of goods and services.
• Therefore, it is classified as a transfer payment.

Last verified on 23-04-2026