How can you synthesise nitric oxide in the laboratory?

Nitrogen forms how many oxides?

Given below are two statements :
Statement $-I :$ The pentavalent oxide of group $-15$ element,$E_2O_5$,is less acidic than trivalent oxide,$E_2O_3$,of the same element.
Statement $-II :$ The acidic character of trivalent oxide of group $15$ elements,$E_2O_3$,decreases down the group.
In light of the above statements,choose the most appropriate answer from the options given below.

Concentrated $HNO_3$ is a yellow-colored liquid due to:

$Y$ in the given sequence of reactions is
$P_4 + x NaOH + y H_2O \xrightarrow{CO_2} X + z NaH_2PO_2$
$X + CuSO_4 \rightarrow Y + H_2SO_4$

Which of the following reactions is incorrect?