The minimum cube strength of concrete used for a pre-stressed member, is________________?
A. 50 kg/cm2
B. 150 kg/cm 2
C. 250 kg/cm2
D. 350 kg/cm2
A. 50 kg/cm2
B. 150 kg/cm 2
C. 250 kg/cm2
D. 350 kg/cm2