The proportion of cement, sand and aggregates for M 20 grade concrete is

• A. 1 ∶ 2 ∶ 4
• B. \(1\;:1\frac{1}{2}\;:3\)
• C. 1 ∶ 3 ∶ 4
• D. 1 ∶ 4 ∶ 3