Identify the correct group of Rabi crops, the true statements about fertilizers, the process for preserving milk, and the term for heat/light.

Here are the solutions to the questions:

1) 4. Choose the correct group of "Rabi Crops"
Rabi crops are sown in winter and harvested in spring.

• a) Wheat, Mustard, Barley, Gram, Pea, Beans - All these are Rabi crops.
• b) Wheat, Gram, Pea, Beans, Pulses - "Pulses" is a broad category, but the others are Rabi.
• c) Rice, Maize, Pulses, Cotton, Groundnuts - These are primarily Kharif crops.
• d) Wheat, Cotton, Barley, Pea, Gram - Cotton is a Kharif crop.

The most accurate group of Rabi crops is option (a).
The correct option is a).

2) Choose the correct statement.

• M) Fertiliser is a chemical substance. (True)
• N) It is nutrient specific and required in very small quantities. (True, compared to manure, and specific nutrients are targeted)
• O) It provides any humus to the soil. (False, manure provides humus, not synthetic fertilizers)
• P) It is soluble in water and readily absorbed by plants. (True, this is how plants take them up)

Statements M, N, and P are correct.
The correct option is c) M, N and P.

3) ______ is the process of preserving milk by first boiling it at 70°C for 15 to 30 seconds and then cooling it quickly.
This process is known as pasteurization, which kills harmful bacteria without significantly altering the milk's quality.
The correct option is d) Pasteurisation.

4) A large amount of heat and light are revolved with a loud sound accompanied by liberation of large amount of gas. It is the type of ______ combustion.
This description perfectly matches an explosion, which is a rapid and violent form of combustion.
The correct option is c) Explosion.

5) Which gas is used in the given picture?
The picture shows a fire extinguisher. Common fire extinguishers use gases like carbon dioxide ($\text{CO}_2$) or nitrogen ($\text{N}_2$) as a propellant or as an extinguishing agent. Oxygen supports combustion, and hydrogen is flammable. Among the given options, nitrogen is an inert gas that can be used in fire suppression systems or as a propellant.
The correct option is a) Nitrogen.

6) Every year 21 March is celebrated as International Day of ______
March 21st is recognized globally as the International Day of Forests.
The correct option is c) Forest.

7) Match and choose the correct option:

• 1. Flora - P) Different plants growing in a particular area.
• 2. Fauna - O) Different animals in a particular area.
• 3. Biosphere - N) part of the earth where living organisms exist.
• 4. Deforestation - M) clearing of forests on a large scale.

Matching these gives: 1-P, 2-O, 3-N, 4-M.
The correct option is b) PONM.

8) The male gamete is called ______ while the female gamete is called ______
In animals, the male gamete is called sperm, and the female gamete is called ovum (or egg).
The correct option is b) sperm, ovum.