Fluorine,chlorine,bromine and iodine are placed in the same group $(17)$ of the periodic table,because

Diagonal relationship is shown by

Consider the following elements arranged in a periodic table segment as shown in the image (Row $1$: $A^{\prime}, B^{\prime}$; Row $2$: $C^{\prime}, D^{\prime}$ where $A^{\prime}$ is above $C^{\prime}$ and $B^{\prime}$ is above $D^{\prime}$). Which of the following is/are true about $A^{\prime}, B^{\prime}, C^{\prime}$ and $D^{\prime}$?
$A$. Order of atomic radii: $B^{\prime} < A^{\prime} < D^{\prime} < C^{\prime}$
$B$. Order of metallic character: $B^{\prime} < A^{\prime} < D^{\prime} < C^{\prime}$
$C$. Size of the element: $D^{\prime} < C^{\prime} < B^{\prime} < A^{\prime}$
$D$. Order of ionic radii: $B^{\prime+} < A^{\prime+} < D^{\prime+} < C^{\prime+}$
Choose the correct answer from the options given below:

Which of the following statement$(s)$ is/are incorrect?

Which of the following pairs shows a diagonal relationship?

What is meant by diagonal relationship?