A closed, filled in dot means that the point is included in the function, so the function has a value at that point.
An open dot means that the point is not included in the function.
f(-2) is asking you for the y-value when x = -2. Looking at the graph, there are two dots at x = -2 (dashed green line). One is open and one is closed. Only the closed point is actually included in the function. The closed point is at y = 1.
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Answer: D) 1