(v) Plaster of Paris is obtained by(a) adding water to calcium sulphate(b) adding sulphuric acid to calcium hydroxide(c) heating gypsum to a very high temperature(d) heating gypsum to 100° C.

The correct answer is (d) heating gypsum to 100° C.

Here are the steps to explain why:

1. Plaster of Paris is a type of building material based on calcium sulfate hemihydrate, nominally CaSO4·0.5H2O.

2. It is created by heating gypsum, a soft, naturally-occurring mineral, to roughly 150 degrees Celsius, which removes three quarters of its water content.

3. Upon addition of water, Plaster of Paris (PoP) becomes regular gypsum (dihydrate) again, causing the material to harden or "set" in ways that are useful for casting and construction.

4. Therefore, the process of obtaining Plaster of Paris involves heating gypsum to a high temperature, but not to a very high temperature. So, the most accurate answer is (d) heating gypsum to 100° C.