The trisubstituted product was synthesized in one step from an electrophilic aromatic substitution of a disubstituted benzene ring. Draw the disubstituted benzene starting material that would give this regioisomeric product.

See explanation and image attached

Explanation:

We know that the substituents that are already present on the benzene ring determine the position of other substituents coming into the ring.

The substituents already present in the ring may be ortho-para or meta directing substituents.

Both -COOH and -NO2 are meta directing because they deactivate the benzene ring towards electrophilic substitution by resonance.

This means that the incoming -Cl electrophile is directed to the meta position. The disubstituted benzene starting material that would give this regioisomeric product must be the one shown in the image attached to this answer.

take a better picture and ill do it