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

The correct answer is: C. 250 kg/cm2

The minimum cube strength of concrete used for a pre-stressed member is 250 kg/cm2. This is according to the Indian Standard Code of Practice for Prestressed Concrete (IS: 1343-1980).

The cube strength of concrete is a measure of its compressive strength. It is determined by testing a concrete cube of 150 mm side under compression. The minimum cube strength of concrete for a pre-stressed member is specified to ensure that the member has adequate strength to resist the loads it will be subjected to.

The other options are incorrect because they are not the minimum cube strength of concrete specified for a pre-stressed member.