Correct Answer - C
When clay ad limestone are strongly heated together, they fuse and react to form cement clinker. This clinker is mixed with 2-3% by weight of gypsum `(CaSO_(4).2H_(2)O)` to form cement. Cement, animportant building material, was discovered by Joseph Aspdin. Hwe noticed that when a strongly heated mixture of limestone ad clay was mixed with water and allowed to stand for some time, it hardened to a stone-like mass resembling portland rock (a popular building stone). he therefore named it portland cement.
