21.Which of the following ingredients of the brick earth enables the brick to retain its shape ?

22.The age of a tree can be known by examining

23.Percentage of silica in a good brick earth lies between

24.Assertion A : Shishum is used for decorative woodwork. Reason R : Shishum can be polished to an excellent finish. Select your answer according to the coding system given below :

25.Excess of alumina in brick earth makes the brick