Questions

* is a dereference operator & is a reference operator. They can be applied any number of times provided it is meaningful. Here p points to the first character in the string "Hello". *p dereferences it and so its value is H. Again & references it to an address and * dereferences it to the value H

Removing the contaminents if any in the water which causes harm to our health is involved in the purifying of water. 

This process involves chemicals. Chloramines, Hydrogen peroxide, Iodine are the chemicals which are used in purifying water.

The possessive form of pronoun ‘one’ is ‘oneself’. So the phrase ‘with himself’ needs to be replaced with ‘with oneself’ to make the sentence grammatically correct. Thus, the correct formation would be, ‘One is often pleased with oneself’.