Answer
If $r\lt0$, the first thought we have is that as the explanatory variable increases, the response variable decreases. But, it also depends on the magnitude of $r$. If $r$ is close to -1, then the given affirmation is correct. But, if $r$ is close to 0, we must say that there is no linear relation between the variables.
Work Step by Step
Notice that, even when $r\approx-1$ we can not say that there is a negative linear relation, but only a negative relation. We must study the residual plot first to conclude whether a linear relation is justified.
