As per Indian Standard code of practice for prestressed concrete (IS 1343 — 1980), the minimum grade of concrete to be used for post tensioned and prestressed. structural
elements are respectively

A

$$M_{20}$$ for both

B

$$M_{40}$$ & $$M_{30}$$

C

$$M_{15}$$ & $$M_{20}$$

D

$$M_{30}$$ & $$M_{40}$$