Which of the following represents the correct order of metallic character of the given elements?

The metallic character of an element depends on its tendency to lose electrons. Metallic character decreases from left to right across a period due to a decrease in atomic size and an increase in ionization energy, while it increases down a group because of an increase in atomic size and a decrease in ionization energy.

Among the given elements, potassium ((K)) belongs to Group 1 and Period 4, making it the most metallic because it loses its valence electron most readily. Magnesium ((Mg)), a Group 2 element in Period 3, is less metallic than potassium but more metallic than beryllium. Beryllium ((Be)), which lies above magnesium in the same group, has a smaller atomic size and higher ionization energy, making it less metallic than magnesium. Silicon ((Si)) is a metalloid located in Group 14 and is the least metallic among the given elements.

Therefore, the correct order of metallic character is

$$Si < Be < Mg < K.$$

Hence, the correct answer is $$\boxed{\text{Option A}}$$.