Step 1: Concept
An element is in the null space if $T(a,b,c) = (0,0)$.
Step 2: Meaning
We need to solve:
$a+b+c = 0$
$a-b-c = 0$
Step 3: Analysis
Adding the two equations: $2a = 0 \Rightarrow a = 0$. Substituting $a=0$ into the first equation: $b+c = 0 \Rightarrow b = -c$.
Step 4: Conclusion
Any vector of the form $(0, b, -b)$ is in the null space. Setting $b=1$ gives the vector (0, 1, -1).
Final Answer: (C)