Which of the following statements are correct ?
i) Boron reacts with concentrated HNO₃ to form nitric oxide and boric acid
ii) Boron reacts with fused NaOH to form boric acid and hydrogen
iii) Boron reacts with SiO₂ to form Si and B₂O₃

(i) Boron reacts with concentrated HNO₃​ to form nitric oxide and boric acid.

$\mathrm{B}+{\mathrm{HNO}}_3+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_3{\mathrm{BO}}_3+\mathrm{NO}$

(ii) Boron reacts with fused Sodium Hydroxide to form Sodium Borate and Hydrogen. 

$\mathrm{B}+6\mathrm{NaOH}\to 2{\mathrm{Na}}_3{\mathrm{BO}}_3+3{\mathrm{H}}_2$

(iii) Boron reacts with SiO₂ to form Si and B₂​O₃  

$4\mathrm{B}+3{\mathrm{SiO}}_2\to 3\mathrm{Si}+2{\mathrm{B}}_2{\mathrm{O}}_3$