46. Potassium Permanganate is used for purifying drinking water, because
(a) it is a sterilising agent
(b) it dissolves the impurities of water
(c) it is a reducing agent
(d) it is an oxidising agent
47. Which of the following is not an isotope of hydrogen?
48. The hardest substance available on earth is
49. Actinides are the elements with atomic numbers from
(a) 97 to 104
(b) 101 to 115
(c) 89 to 103
(d) 36 from 43
50. Which metal pollute the air of a big city?