Why closed loop differential amplifiers are difficult to null?

Why closed loop differential amplifiers are difficult to null? Correct Answer Due to compensating network

The closed loop differential amplifiers are more difficult to null because the use of compensating network can change the common mode rejection mode.

Related Questions

Point out the error (if any) in the following C code?
#include #include int main(void){ int* p = NULL; struct S *s = NULL; void(*f)(int, double) = NULL; char *ptr = malloc(15); if (ptr == NULL) printf("Out of memory"); free(ptr);}