Consider elements A', B', C', D' where A' and B' are in Period 2, C' and D' in Period 3; A' and C' are in Group 1, B'…

🧠 Decode the abstract labels first — A' = Li, B' = Be, C' = Na, D' = Mg The question gives Period and Group placements. A' (P2, G1) = Li, B' (P2, G2) = Be, C' (P3, G1) = Na, D' (P3, G2) = Mg. Translate before reasoning.

🗺️ Check each statement A — Atomic radii: $B' < A' < D' < C'$ → Be < Li < Mg < Na. Group 2 is smaller than Group 1 in the same period. Period 2 is smaller than Period 3 in the same group. Both rules satisfied. True.

B — Metallic character: same order $B' < A' < D' < C'$. Metallic character tracks atomic size: a bigger atom loses its electron more easily. Same reasoning as A. True.

C — Size: $D' < C' < B' < A'$ → Mg < Na < Be < Li. This puts Period 3 atoms smaller than Period 2 atoms — that is wrong. Period 3 elements have an extra shell. False.

D — Ionic radii: $B'^{2+} < A'^+ < D'^{2+} < C'^+$ → $\ce{Be^{2+}} < \ce{Li^+} < \ce{Mg^{2+}} < \ce{Na^+}$. Standard values: $\ce{Be^{2+}} = 45\,\text{pm}$, $\ce{Li^+} = 76$, $\ce{Mg^{2+}} = 72$, $\ce{Na^+} = 102$. So $45 < 76 \approx 72 < 102$. The order matches. True.

True statements: A, B, D.

⚠️ The trap Statement C looks similar to A but the order is reversed. Reading too fast, you might mark C as "the same trend". Always re-read each statement carefully before agreeing.

$\boxed{\text{Answer: (b)}}$