21.Compared to mild steel, cast iron has i) high compressive strength ii) high tensile strength iii) low compressive strength iv) low tensile strength The correct answer is

22.The basic purpose of a retarder in concrete is

23.The stretcher bond in brick masonry can be used only when the thickness of wall is

24.Three basic raw materials which are needed in large quantities for production of steel are

25.Which of the following should be used for hearting of thicker walls ?