Non-negative x-values would start at x = 0 and move to the right.
A function can be determined with the vertical line test. That is, if a vertical line is passed through the graph and it hits in more than one point, it is not a function. In other words, each x-value can match up with only one other y-value.
A.) is a function whose domain consists of both positive and negative real numbers.
B.) Is not a function
D.) is a function whose domain consists of negative real numbers and zero
C.) is a function whose domain is the set of non-negative real numbers.
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