- C$_3$S (Tricalcium silicate) contributes to early age strength (P) and gives the highest heat of hydration (S), as it reacts quickly with water.
- C$_2$S (Dicalcium silicate) is responsible for later age strength (Q) and has the lowest heat of hydration (T), as it hydrates more slowly than C$_3$S.
- C$_3$A (Tricalcium aluminate) causes flash setting (R) and contributes to high heat of hydration (S) because it reacts rapidly with water.
Thus, the correct combination is:
\[
\boxed{\text{(A) (i) - (P), (ii) - (Q) and (T), (iii) - (R) and (S)}}.
\]