The correct answer is D. All the above.
Porcelain is a type of ceramic that is made from a mixture of clay, feldspar, and quartz. The clay used in porcelain must be sufficiently pure, of high degree of tenacity, and of good plasticity.
Sufficient purity is important because any impurities in the clay can affect the quality of the porcelain. For example, iron impurities can cause the porcelain to turn yellow.
High degree of tenacity is important because it allows the clay to be shaped without breaking. The clay must be strong enough to withstand the forces that are applied to it during the manufacturing process.
Good plasticity is important because it allows the clay to be molded into the desired shape. The clay must be able to be easily shaped and manipulated without breaking.
If any of these three qualities are not met, the quality of the porcelain will be affected. Therefore, it is important to use clay that is sufficiently pure, of high degree of tenacity, and of good plasticity when making porcelain.