The correct order of metallic character is:

🧠 Metallic character grows left and grows down — pick the element farthest to the left and lowest in the group Metallic character is just "how easily this atom loses an electron". Bigger atoms with fewer protons lose electrons more easily. So down-and-left wins.

🗺️ Compare all three K: Group 1, Period 4. Largest atom of the three, only 1 valence electron — most metallic. Ca: Group 2, Period 4. Same period as K but one column to the right. Slightly less metallic than K. Be: Group 2, Period 2. Two periods above Ca, much smaller — least metallic.

Two pairs to settle: K vs Ca (same period): K is Group 1, Ca is Group 2. K wins. Ca vs Be (same group): Ca is below Be. Ca wins.

Order: $\ce{K} > \ce{Ca} > \ce{Be}$.

⚠️ The trap Don't compare K and Be by atomic number alone. Be ($Z=4$) and K ($Z=19$) — students sometimes assume "lower Z = more metallic" because alkali metals are at low Z within a period. That logic only works within the same period. Across different periods, the period number dominates.

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