Shine at freshly cut sodium is because of:
A. due to oscillations of free electrons.
B. due to weak metallic bonding.
C. due to absorption of light in crystal lattice
D. due to the presence of free valency at the surface.

Hint: Sodium is a soft metal, belonging to group A, which can be cut easily by a knife. It is highly reactive.Sodium is a chemical element with the symbol Na (from Latin "natrium") and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table.

Complete step by step answer:
When we cut a block of sodium metal a surface gets exposed which is shining. It is due to the fact that sodium (\[{\text{Na}}\]) has electronic configuration as \[2,8,1\]. This \[1\] electron in the last orbital is the valence electron or free electron, which oscillates in the atom. These oscillating free electrons reflect the light and this reflection results in a shiny appearance of sodium surface. But this shiny effect is temporary as sodium is highly reactive, it reacts with the oxygen present in the air and forms a white layer of sodium oxide which stops further reaction between metal and oxygen.
So, option (A) is correct.

Additional information: Sodium element belongs to the alkaline earth metal, it displaces the hydronium ion when it reacts with water.
The property of metal to appear shiny either on the outside or inside is known as lustrous.

Note:
There will be reflection of light rather than absorption. The shiny effects start to diminish as the metal remains in contact with oxygen which leads to formation of white layer called sodium oxide which appears grey in color.