A British electronics manufacturer has built a factory in which quartz crystals can be grown in 3 weeks. The natural growth of quartz takes 3 million years, and very often the crystals are not sufficiently pure to satisfy the precise needs of science. However, the manufactured crystals are exceptionally pure, and this is important because quartz, in transistors is used in an astonishing number of devices where constant accuracy is required: radio and television transmitters and receivers, space satellites and computers are familiar examples. In order to make artificial quartz, very small pieces of the natural crystal imported from Brazil are placed in long, narrow, steel cylinders. A high pressure and a high temperature are maintained within the cylinders for 3 weeks, and at the end of this the small fragments have grown to the required weight of one pound. The quartz is then ready to be made into the tiny transistors that have replaced the much larger thermionic valves.
The manufactured crystals have to be pure
-
A.
because natural quartz is pure -
B.
to maintain hygiene in factory work -
C.
to satisfy the precise needs of importers -
D.
to satisfy the exact requirements of science -
E.
otherwise they would take 3 million years to grow.