To solve this question, let's evaluate both the assertion and the reason, and see if they explain the situation in the context of 'C' programming structures.

• Assertion (A): In 'C', structures cannot be compared using relational operators == and !=.
  • This assertion is true because, in C, structures are complex data types, and direct comparison using == and != is not allowed. These operators are meant for comparing fundamental data types like int, float, char, etc., not aggregates like structures.
• Reason (R): A field by field comparison might require unacceptable amounts of repetitive code for large structures. Pointer fields may also cause problems.
  • The reason is also true. For structures, you need to manually compare each field if you want to determine equality. This can be tedious and error-prone, especially for structures with many fields or nested structures.
  • Additionally, structures with pointer fields present issues because they hold memory addresses rather than actual data. Thus, comparing pointers involves checking memory addresses, which may not reflect the actual data equality.

Given the assertions and reasons provided, we can conclude:

• Both Assertion (A) and Reason (R) are true.
• Reason (R) directly explains why Assertion (A) is true. It highlights the problem with comparing structures directly using == and != due to the complexity involved in field-by-field comparison and complications arising from pointer fields.

Therefore, the correct answer is: Both (A) and (R) are true and (R) is the correct explanation of (A).