"The difference between the length of a certain brass rod and that of a steel rod is clamped to be constant at all temperatures". The above statement

• A. can never be true
• B. can be valid only for temperatures below 0?C
• C. can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod
• D. can be true provided their lengths are directly proportional to the linear coefficients of the material of the rod
• E. None of the above