Step 1: Concept
The integral of a step function is the sum of (value $\times$ width) for each interval.
Step 2: Meaning
Intervals: $[-3,-2], [-2,-1], [-1,0], [0,1], [1,2], [2,3]$ with widths of 1 unit.
Step 3: Analysis
Values: $(-3 \times 1) + (-2 \times 1) + (-1 \times 1) + (0 \times 1) + (1 \times 1) + (2 \times 1)$.
Step 4: Conclusion
$-3 - 2 - 1 + 0 + 1 + 2 = -3$.
Final Answer: (A)