Question

given the statement \if a line is horizontal, then it has slope equal to zero,\ what is its contrapositive?
○ if a line is horizontal, then it has zero slope.
○ if a line has zero slope, then it is a horizontal line.
○ if a line is not horizontal, then it does not have zero slope.
○ if a line does not have zero slope, then it is not a horizontal line.

Explanation:

A contrapositive of a statement "If P, then Q" is "If not Q, then not P". Here, P is "a line is horizontal", Q is "it has slope equal to zero". So not Q is "a line does not have zero slope", not P is "it is not a horizontal line".

Answer:

If a line does not have zero slope, then it is not a horizontal line.