Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Lithium and beryllium unlike their other respective group members form compounds with pronounced ionic character. Reason $(\mathbf{R})$ : Lithium and Magnesium have similar properties due to diagonal relationship. In the light of the above statements, choose the correct answer from the options given below:

• A

  Both $(\mathbf{A})$ and $(\mathbf{R})$ are true and $(\mathbf{R})$ is the correct explanation of $(\mathbf{A})$.
• B

  Both $(\mathbf{A})$ and $(\mathbf{R})$ are true but $(\mathbf{R})$ is not the correct explanation of $(\mathbf{A})$.
• C

  (A) is true but (R) is false.
• Correct answer
  D

  (A) is false but $(\mathbf{R})$ is true.

Hence, the correct answer is option: 'D'.