Answer: Option B. -> Direct cause of water pollution
:
B

  $\bullet$ Manures are the organic substances obtained by the decomposition of animal excreta and plant waste. Adding manure is a natural way of increasing soil fertility and in turn increasing yield.
  $\bullet$ Fertilisers are artificially synthesised inorganic salts which also increase yield. Excessive use of fertilisers kill the micro-organisms present in the soil. They runoff into the nearby water bodies which would result in water pollution.

Answer: Option B. -> To prevent absorption of excess moisture.
:
B, C, and D
Grain production is seasonal but its consumption is continuous. They have to be protected from unfavourable weather, moulds, harmful microorganisms, moisture, insects, rodents, birds and other contaminants. Hence, in order to maintain grain quality and quantity for long periods, storage of grains require chemical treatment which protects them from pests, microorganisms and moisture.

Answer: Option B. -> Combine
:
B

Cutting of the crop close to the ground after it matures is called harvesting. Farmers with small farms harvest their crops manually using tools like a sickle. However, after harvesting, they need to manually undertake threshing and winnowing. Whereas, farmers with huge farms cannot deploy manual labour for harvesting and threshing as it is more time consuming. Instead, it is more efficient for them to use machines such as a combine. A combine performs the function of both harvester as well as thresher. This saves a lot of time and manual labour.

Answer: Option B. -> Weedicides
:
A, B, and D

Weeding is the process of removal of unwanted plants(weeds) that grow along with the crops. Removal of weed is necessary as they compete with the main crops for nutrients, sunlight and water.
It should be done in an early crop stage. It can be done manually, using tools like khurpi, or can be done using seed drills. Weedicides like 2,4-D can also be used. But their use should be restricted as they are synthetic and are poisonous. They can adversely affect the health of the farmers.

Answer: Option B. -> Immersing the grains in water.
:
B

The most appropriate and simple method of separating good quality grains from the damaged ones is by immersing all the grains in water. Doing this will cause damaged or bad grains to float up because they are hollow. The viable or good seeds, on the other hand, will sink and settle at the bottom.

Answer: Option B. -> Drip system
:
B

Drip irrigation is a technique in which water flows through a filter into special drip pipes. It helps in releasing water drop by drop into the soil near the roots of plants. In contrast to other types of irrigation systems such as overhead sprinklers, water can be more precisely applied to the plant roots. If designed, installed and managed properly, this method contributes greatly to water conservation by reducing evaporation.

Answer: Option A. -> True
:
A

A fallow field is a land that a farmer ploughs but does not cultivate for one or more seasons to allow the field to regain its fertility naturally. They allow animals such as sheep, goats to graze. Their droppings will enrich the soil.
This practice of leaving fields fallow, dates back to ancient times when farmers realised that using soil continuously depleted its nutrients.

Answer: Option A. -> Kharif and rabi crops
:
A
The crops grown during rainy season (June to September) are known as kharif crops (e.g. paddy, maize, soyabean etc) while those grown in winter season (October to March) are known as rabi crops (e.g. wheat, gram, pea etc).

Answer: Option A. -> compost
:
A
Composting is a process in which organic wastes are decomposed naturally to form a nutrient-rich compost. It is a natural and environment-friendly process, which forms a key feature in organic farming. Organic substances like animal faeces, leaves, grass clippings, vegetables, eggshells, etc., can also be composted and used in farms.

Answer: Option A. -> Winnowing is the process of separating grain from chaff.
:
A and C
  $\bullet$ Grain can be separated from chaff by a method called winnowing. In its simplest form, it involves throwing the mixture into air so that the wind carries away the light chaff, while the heavier grains fall down for recovery. There is no loss of fodder in the process of winnowing. Since it is done manually it is time-consuming.
  $\bullet$ The process of loosening grains or seeds from husk is called threshing. It is done before winnowing. Modern equipment used for threshing may cause fodder loss.