Xavier Aptitude Test 2024 Paper

Consider the system of two linear equations as follows: $3\mathit{x}+21\mathit{y}+\mathit{p}=0$; and $\mathit{q}\mathit{x}+\mathit{r}\mathit{y}-7=0$, where $\mathit{p},\mathit{q}$, and $\mathit{r}$ are real numbers.
Which of the following statements DEFINITELY CONTRADICTS the fact that the lines represented by the two equations are coinciding?