Correct option is C
The strength of compression members subjected to axial compression is defined by curves corresponding to
classes a, b, c, and d. These curves are used in structural engineering to determine the buckling strength of compression members based on their cross-sectional shapes and dimensions.
e, f, g: Incorrect, as these do not correspond to the standard classes for compression members.
b, e, f: Incorrect, as these do not cover all the necessary classes.
a, b, c and d: Correct, as these are the standard classes used to define the strength of compression members.
a, d: Incorrect, as this only includes part of the required classes.
Therefore, the correct answer is (c) a, b, c and d.
