To answer this question, let's analyze the given sequence:
1 = 5
2 = 25
3 = 125
4 = 625
Looking at the pattern, we can see that each number in the sequence is obtained by raising the corresponding number to the power of 5.
So, 5 raised to the power of 1 is 5, 5 raised to the power of 2 is 25, 5 raised to the power of 3 is 125, and 5 raised to the power of 4 is 625.
Therefore, the next number in the sequence would be 5 raised to the power of 5, which is 3125.
Hence, the correct answer is option A) 3125.