A: Root Cause Analysis: Looking at the given vulnerable code line and its context, the CWE-476 (NULL Pointer Dereference) vulnerability exists in the code because both `a` and `b` are pointers to memory that is assumed to be valid and dereferenced. However, there is no check for the case where either `a` or `b` is NULL, which could lead to a NULL pointer dereference and undefined behavior.