What Are the Two Major Problems with the Benchmark Technique

What are the two major problems with the benchmark technique of measuring algorithm efficiency?

A) Different hardware platforms have different processing speeds, meaning the running times will differ.
B) A benchmark test does not account for differences in the size of data sets.
C) The test cannot be performed without modifying the code for which the benchmark will be performed on.
D) It can be impractical to determine the running time for algorithms with very large data sets.