A set is a well-defined collection of objects.
There are two methods of representing a set

• Roster or Tabular form In the roster form, we list all the members of the set within braces { } and separate by commas.
• Set-builder form In the set-builder form, we list the property or properties satisfied by all the elements of the sets.

According to the narrator, young people in the village are ignoring their mother tongue Kannada and speaking in English, which is a disgraceful event.  Rama Rao's son speaks in English to the old woman selling firewood.  She does not understand his words and goes away muttering abuses for wasting her time.  Rama Rao's son felt it against his prestige that he should talk in Kannada to a poor woman.

The narrator refers to Ranga's courtyard as the Black Hole of Calcutta because the teeming masses had congested that small space into a similar sort of structure where more and more people seemed to be swallowed up as they went in. The Black Hole of Calcutta was a dungeon in the old Fort of William of Calcutta where British prisoners of war were held captive by the nawab of Bengal, Siraj-ud-Daulah. The inhabitants had to live in close quarters, crammed together in a small space. The situation was similar in Ranga's courtyard which had witnessed a huge turnout due to the arrival of the accountant's son from the city.

The old lady ran her hand over Ranga’s chest and looked into his eyes. She was satisfied to find the sacred thread still on him. She was happy that he had not lost his caste.

Ranga’s homecoming was a great event. The crowds milled around his house to see whether he had changed or not. People were quite excited as the boy was returning home after studying English at Bangalore. Everyone was surprised to see that Ranga was the same as he had been six months ago, when he had first left the village.

Ten years ago, the English language was not very popular in the village. People hardly knew how to speak in English. Only, Ranga's father had the courage to send his son to Bangalore to study. This was therefore a great event.

The narrator lived in a small village hosahalli in the state of Karnataka.
The narrator said there is not even a shadow of their village on the map and there are mango trees in his village are famous for their sourness.
Narrator means merely eating these fruit can make anyone cough.

The Peninsular Block is made up of a series of patland plateaus such as the Hazaribagh plateau, the Palamu plateau, the Ranchi plateau, the Malwa plateau, the Coimbatore plateau, and the Karnataka plateau. The northern boundary of the Peninsular Block may be taken as an irregular line running from Rann of Kachchh along the western flank of the Aravali Range near Delhi and then roughly parallel to the Yamuna and the Ganga as far as the Rajmahal Hills and the Ganga delta.

Chemistry has a direct impact on our life and has wide range of applications in different fields. These are given below:
(A) In Agriculture and Food:
(i) It has provided chemical fertilizers such as urea, calcium phosphate, sodium nitrate, ammonium phosphate etc.
(ii) It has helped to protect the crops from insects and harmful bacteria, by the use ‘ of certain effective insecticides, fungicides and pesticides.
(iii) The use of preservatives has helped to preserve food products like jam, butter, squashes etc. for longer periods.
(B) In Health and Sanitation:
(i) It has provided mankind with a large number of life-saving drugs. Today, dysentery and pneumonia are curable due to discovery of sulpha drugs and penicillin life-saving drugs. Cisplatin and taxol have been found to be very effective for cancer therapy and AZT (Azidothymidine) is used for AIDS victims.
(ii) Disinfectants such as phenol are used to kill the micro-organisms present in drains, toilet, floors etc.
(iii) A low concentration of chlorine i.e., 0.2 to 0.4 parts per million (ppm) is used ’ for sterilization of water to make it fit for drinking purposes.
(C) Saving the Environment:
The rapid industrialisation all over the world has resulted in lot of pollution.
Poisonous gases and chemicals are being constantly released in the atmosphere. They are polluting environment at an alarming rate. Scientists are working day and night to develop substitutes which may cause lower pollution. For example, CNG (Compressed Natural Gas), a substitute of petrol, is very effective in checking pollution caused by automobiles.
(D) Application in Industry:
Chemistry has played an important role in developing many industrially ^ manufactured fertilizers, alkalis, acids, salts, dyes, polymers, drugs, soaps,
detergents, metal alloys and other inorganic and organic chemicals including new materials contribute in a big way to the national economy.
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In a true experiment, participants are randomly assigned to either the treatment or the control group, whereas they are not assigned randomly in a quasi-experiment. ... Thus, the researcher must try to statistically control for as many of these differences as possible. Quasi-experimental research involves the manipulation of an independent variable without the random assignment of participants to conditions or orders of conditions. Among the important types are nonequivalent groups designs, pretest-posttest, and interrupted time-series designs. In a true experiment, each participant who volunteered would have an equal chance of being assigned to any of the three groups. Quasi-experiments are employed when the researcher is interested in independent variables that cannot be randomly assigned.