The answer is d. 10 to the fifth the way you found out is just count how many places the decimal point has moved. It’s moved 5 places so it could be 10 to the 5 or 10 to -5 but since it moved to the right it’s 10 to the 5. If it moved to the left five places then instead of 723,000 it would be 0.0000723.
Hope this helps on this problem and future problems.