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 B. Negative
Step-by-step explanation:
The slope is the ratio of a change in y-value to the corresponding change in x-value. When the line goes down to the right, as here, the y-value change is negative when the change in x is positive. Hence the ratio of changes is negative, and the slope is negative.
The various cases are ...
 up to the right: positive slope
 horizontal line: 0 slope
 down to the right: negative slope . . . . what we have here
 vertical line: undefined slope