Answer: Option A. ->
:

Reason: 2 Marks
Example: 1 Mark
Open drain system serves as a breeding place for flies, mosquitoes, and organisms which cause diseases. Hence open drainage is never opted for when planning for a town.
Example:
Chandigarh being a planned city doesn't have any open drainage system. Instead, the city has a well planned underground network of pipes for disposal of sewerage. The system has been designed according to the natural slope of the city for sewage to flow under gravity.

Answer: Option A. ->
:
Correct matching: 0.5 marks each
$\begin{array}{cc}a)Cleaningofwaterisaprocessof& ii)removingpollutants\\ b)Wastewaterreleasedbyhousesiscalled& v)sewage\\ c)Driedsludgeisusedas& iv)manure\\ d)Drainsgetblockedby& vi)cookingoilsandfats\\ e)Wastewateristreatedin& i)sewagetreatmentplant\\ f)Septictanks,chemicaltoilets,compostingpitsareexamplesof& iii)lowcostdisposalsystems\end{array}$

Answer: Option A. ->
:

Naming: 1 Mark each
Organic impurities in sewage include:
1) Human faeces
2) Herbicides
3) Fruit and vegetable wastes

Answer: Option A. ->
:

Vermi-processing toilet: 4 Marks
Reason: 1 Mark
Vermi refers to small worms such as earthworms. Vermi-processing toilets are those toilets in which humans excreta is treated by earthworms. It has been found to be a novel, low water-use toilet for safe processing of human excreta without odour and fly problem. The operation of the toilet is very simple and hygienic. The human excreta is completely converted to vermi cakes - a resource much needed for enhancing the fertility of the soil.
We should not throw chemicals like paints, solvents, insecticides, motor oil, medicines down the drain as they may kill microbes that help purify water. It also leads to pollution of groundwater and may adversely affect the health of organisms.

Answer: Option A. ->
:
Each point: 1 Mark
i) Many cities have large and growing population resulting in greater demand for water resources. A large population means, not only more water is required for domestic use but also for higher foodgrain productivity. 
ii) Today the multinational companies and other industrial units consume large quantities of hydroelectric power and for the processing of which they put greater pressure on the existing freshwater resources.
iii) Pollution of water bodies due to the discharge of industrial effluents, use of pesticides, insecticides, and fertilizers used in agriculture, make the river water hazardous for human consumption.
iv) Inefficient use of water for agriculture is another reason for scarcity of freshwater. Traditional techniques of irrigation cause maximum water loss due to evaporation, drainage, percolation, water conveyance, and excess use of groundwater.
v) Reduction in traditional water recharging areas. Rapid construction is ignoring traditional water bodies that have also acted as groundwater recharging mechanism.

Answer: Option A. ->
:

a) 2 Marks
b) 3 Marks
a) Water pollution refers to the mixing of contaminants or pollutants into the water bodies (sea, lakes, rivers, oceans, groundwater, etc) through direct or indirect discharges which causes environmental degradation and affects whole biosphere.
Sources of water pollution are: domestic waste and sewage, hot water released from cooling power plants.
b) Sewage is a mixture of wastewater coming out of homes and other places.
    Sewers are pipes which carry sewage.
    Sewerage is a network of sewage carrying pipes.

Answer: Option D. -> Hampers health as the water is impure
:
D

Our day to day actions that need serious contemplation is often ignored. Be it dumping the waste and construction debris on road or pushing the road sweeping into the nearby drain, every incoherent action leads to worsening of the state of the drainage system. If the drain slabs are not repaired on time, leaving convenient openings for pushing garbage and trash matter inside the drain. The open drains are treated as garbage store, which when are completely filled up, fail to carry any storm flow and contribute to water-logging and flooding. To aggravate the situation these flooded or waterlogged areas serve as the abode for vectors that spread diseases like malaria, filarial or dengue.

Answer: Option C. -> Wastewater from homes is fit for consumption.
:
C

The wastewater includes human waste, food scraps and chemicals. Sewage is a type of wastewater that comprises of domestic wastewater. It can contain food waste, waste from toilets, etc. and hence, is unfit for consumption. Wastewater from industries can contain chemicals and toxic wastes.

Answer: Option C. -> pollutants
:
C
Sewage is a complex mixture containing suspended solids, organic and inorganic impurities.
These pollutants are removed using physical, chemical, biological processes in a wastewater treatment plant before they are released into a water body.

Answer: Option A. -> True
:
A

Cooking oil and fats get hardened and therefore can block pipes. In open drains, the fats clog the soil pores which reduces its effectiveness in filtering water.