Cr-50, Cr-52, Cr-53, and Cr-54.
The average atomic mass of chromium is = 51.996 amu.
Cr-52 is the answer.
Cr-52 because its mass number is closest to the actual atomic mass of Chromium (51.996).
Point is the more abundant an isotope is, the average will shift more towards its atomic mass.
51.996 is more close to Cr-52