According to IS : 456 -1978, the modulus of elasticity of concrete Ec (in N/mm2) can be taken as______________?

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According to IS : 456 -1978, the modulus of elasticity of concrete Ec (in N/mm2) can be taken as______________?

A. Ec = = 5700
B. Ec = = 570
C. Ec = = 5700fck
D. Ec = where fck N/mm2 = 700 is the characteristic strength in