General Science – Exercise – 1

26. The two elements that are frequently used for making transistors are

(a) boron and aluminium
(b) silicon and germanium
(c) iridium and tungsten
(d) niobium and columbium

27. The gases used in different types of welding would include

(a) oxygen and hydrogen
(b) oxygen, hydrogen, acetylene and nitrogen
(c) oxygen, acetylene and argon
(d) oxygen and acetylene

28. Permanent hardness of water may be removed by the addition of

(a) sodium carbonate
(b) alum
(c) potassium permanganate
(d) lime

29. Heavy water is

(a) deuterium oxide
(b) PH7
(c) rain water
(d) tritium oxide

30. The gas usually filled in the electric bulb is

(a) nitrogen
(b) hydrogen
(c) carbon dioxide
(d) oxygen

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