Which among the following is the correct composition of Borax?

Borax, chemically represented as $\mathrm{Na}_2 \mathrm{ B}_4 \mathrm{O}_7$. $10 \mathrm{H}_2 \mathrm{O}$, consists of sodium $(\mathrm{Na})$, boron (B), oxygen $(\mathrm{O})$, and hydrogen $(\mathrm{H})$. It is a white, crystalline mineral and a common household chemical known for its various uses, including as a cleaning agent, insecticide, and in the manufacture of glass and ceramics. Borax dissolves easily in water, forming an alkaline solution due to its basic nature.