Out of the constituents of cement namely,tricalcium silicate ($$C_2S$$), dicalcium silicate ($$C_2S$$), tri calcium aluminate ($$C_3A$$) and tertracalcium alumino ferrite ($$C_4AF$$) the first to set and harden is

A

$$C_4A$$

B

$$C_4AF$$

C

$$C_3S$$

D

$$C_2S$$