When chromium loses two electrons, its configuration changes to

A. [Ar]4s13d5.

B. [Ar]4s1.

C. [Ar]4s13d4.

D. [Ar]3d4.

Electronic configuration of cromium is

Cr-[Ar]4s¹3d⁵

When cromium loses two electrons it becomes Cr⁺².

So its electronic configuration becomes,

Cr⁺²-[Ar]3d⁴

One electron will go from 4s orbital and one electron will go from 3d orbital.

So the answer here is D. [Ar]3d⁴ - because after losing 2 electrons electronic configuration of cromium becomes [Ar] 3d⁴.