Correct option is B
The
characteristic strength of concrete, as defined by IS 456:2000, is the strength below which not more than
5% of the test results are expected to fall.
For M20 concrete, the characteristic compressive strength at 28 days is
20 MPa.
Out of 100 cubes, it is expected that
95 cubes will have compressive strength
greater than 20 MPa, while
5 cubes may have strength
less than or equal to 20 MPa due to natural variability in concrete properties.
