Answer:
His slope should be positive because the trend line is slanted up to the right.
Step-by-step explanation:
Assume the graph is like the one below.
The line is slanted up and to the right, so the slope is positive.
A is wrong. The points could all be positive and have a negative slope.
C is wrong. Most of the points are not on the line but the slope is still positive.
D is wrong. The slope does not depend on the values of x and y. It depends on the values of Δx and Δy.