Answer :

To determine what 6.8 decreased by 100% is, let's follow a step-by-step approach:

1. Understand what it means to decrease a number by 100%:
- Decreasing a number by 100% means reducing the value by its entire amount. In other words, subtracting the whole value from itself.

2. Calculate the amount of decrease:
- If we start with 6.8, decreasing it by 100% would involve subtracting 100% of 6.8.
- 100% of 6.8 is simply 6.8.

3. Apply the decrease to the initial value:
- Subtract the amount of decrease from the initial value:
[tex]\[ 6.8 - 6.8 = 0 \][/tex]

Hence, when 6.8 is decreased by 100%, the result is [tex]\(0\)[/tex].

So, the correct option is:
(A) 0