Which of the following is TRUE regarding stress-strain curve of concrete?

A

A straight line up to the failure.

B

Hyperbolic up to 0.002% strain value and then a straight line up to failure.

C

Parabolic up to 0.002% strain value and then a straight line up to failure.

D

Straight line up to 0.002% strain value and then parabolic up to failure.