Hamming distance is a measure of the difference between two strings of equal length. It is calculated by counting the number of positions at which the corresponding elements in the two strings are different. In this case, the two strings are "001111" and "010011", both of length 6.

Calculating the Hamming Distance:
To calculate the Hamming distance between the given strings, we need to compare the corresponding elements at each position and count the differences.

1. Compare the first position:
- The first element of the first string is "0".
- The first element of the second string is "0".
- Both elements are the same, so there is no difference at this position.

2. Compare the second position:
- The second element of the first string is "0".
- The second element of the second string is "1".
- Both elements are different, so there is a difference at this position.

3. Compare the third position:
- The third element of the first string is "1".
- The third element of the second string is "0".
- Both elements are different, so there is a difference at this position.

4. Compare the fourth position:
- The fourth element of the first string is "1".
- The fourth element of the second string is "0".
- Both elements are different, so there is a difference at this position.

5. Compare the fifth position:
- The fifth element of the first string is "1".
- The fifth element of the second string is "1".
- Both elements are the same, so there is no difference at this position.

6. Compare the sixth position:
- The sixth element of the first string is "1".
- The sixth element of the second string is "1".
- Both elements are the same, so there is no difference at this position.

Counting the Differences:
From the above comparisons, we can see that there are 3 positions where the corresponding elements in the two strings are different. Therefore, the Hamming distance between "001111" and "010011" is 3.

Answer:
The correct answer is option 'C', which states that the Hamming distance between "001111" and "010011" is 3.