Which of the following amines acts as the strongest base?

Nitration of aniline in a strong acidic medium gives a significant amount of $m$-nitroaniline because:

With respect to the following reaction,consider the given statements:
$C_6H_5NH_2 \xrightarrow{HNO_3, H_2SO_4, 288 \ K} \text{products}$
$(A)$ $o$-Nitroaniline and $p$-nitroaniline are the predominant products.
$(B)$ $p$-Nitroaniline and $m$-nitroaniline are the predominant products.
$(C)$ $HNO_3$ acts as an acid.
$(D)$ $H_2SO_4$ acts as an acid.

During the acetylation of amines,what is replaced by acetyl groups?

Which of the following will give $N_2$ gas on treatment with nitrous acid?

In the reaction $CH_3NH_2 + X + KOH \rightarrow CH_3NC + 3KCl + 3H_2O$,what is $X$?