Bromobenzene in the presence of nitronium ions preferentially forms para-bromonitrobenzene rather than the meta or the ortho product. This means the reaction is .

Electrophilic aromatic substitution is the reaction in which the bromobenzene is present with the presence of the nitronium ions and results in the formation of para-bromonitrobenzene.

Explanation:

Bromobenzene in the presence of nitronium ions preferntially forms para-bromonitrobenzene rather than meta or the ortho product.

so. here the reaction been mentioned refers to Electrophilic  aromatic substitution.

Electrophilic  aromatic substitution: An organic reaction is referred as the aromatic substitution.

In this type of organic reaction a system is present which is an organic system to which an atom gets attached which get replaced by an electrophile.

It is one of the most important reactions of the field synthetic organic chemistry.

the usage of these reactions are in synthesis of the most important intermediates which are used as the precursors in agrochemical, industrial and pharmaceutical products.

c. orbital shape i hope this is correct