Questions

The point or place of origin of an earthquake is called Focus. 

And,

The point where the seismic waves reach the surface is called as Epicenter.

The relative pronoun acts as the subject or object of the relative clause. It replaces words like she, he, him, her, they, them etc.

It is, therefore, wrong to repeat the pronoun in the relative clause.

Hence, the correct sentence is Shreya, who is my best friend, is a singer.

In India, Islamic rulers Qutb-ud-din Aibak imposed jizya on non-Muslims first time which was called kharaj-o-jizya. Jizya was abolished by the Mughal ruler Akbar in the 16th century but was re-introduced by Aurangzeb in the 17th century.

In the given puzzle, the logic followed is

First digits comes from the number of letters in the word

Second digit is its serial number

Third digit is the addition of first and second digits

=> SUNDAY = 6713

Here all the given options are Exothermic reactions. Exothermic reactions are those reactions which involves the release of heat.

Generally all the combining reactions are exothermic in nature.