Let's go through these one by one to see if they are true or not.
A. This is true because a positive slope goes uphill as you read from left to right. In other words, as x gets bigger, so does y. They increase together.
B. This is true as well. The change in y (aka "rise") is zero because we haven't gone up or down. A perfectly level horizontal line always has a slope of zero.
C. This is true. A vertical line always has an undefined slope. Recall that slope = rise/run. For any vertical line, there is no change in x so the run is 0. You cannot divide by zero; hence the undefined result.
D. This is false. This contradicts choice A above, which says that a positive slope is the result of going uphill as you read from left to right. In this case, we have a negative slope going downhill in the same reading direction.
Final Answer: Choice D
