61.
Which of the following is used in welding broken pieces of iron rails and machine parts?

62.
Of the following commonly used materials, the one that is not an alloy is

63.
The manufacture of iron from iron ore involves the process of

65.
The important ore of aluminium is

66.
Which of the following elements is not present in stainless steel?

67.
Which one of the following minerals is found in pure form?

68.
What is the principal ore of aluminium ?

69.
Burning pyrites ore gives out

70.
Which one of the following pairs is not correctly matched?