Reasoning

First term = 6*2 = 12. Second term = 6² – 1 = 35. Third term = 8*2 = 16. Fourth term = 8² – 1 = 63.

A sponge is a porous material. Rubber is an elastic material. (Choice a) is incorrect because rubber would not generally be referred to as massive. The answer is not (choice b) because even though rubber is a solid, its most noticeable characteristic is its elasticity. Choice d is incorrect because rubber has flexibility.