The functional group that shows negative resonance effect is:

Identify the functional group that shows negative resonance effect ($$-R$$ effect).

What is the negative resonance effect ($$-R$$ effect)?

A group shows $$-R$$ effect when it withdraws electron density from the conjugated system through resonance. These groups typically have a multiple bond to an electronegative atom (like $$C=O$$), which pulls electron density away from the attached system.

What is the positive resonance effect ($$+R$$ effect)?

Groups with lone pairs on the atom directly bonded to the conjugated system can donate electron density through resonance. Examples: $$-NH_2$$, $$-OH$$, $$-OR$$.

Analyzing each option:

$$-NH_2$$: Has a lone pair on N that can be donated to the ring. Shows +R effect.

$$-OH$$: Has lone pairs on O that can be donated. Shows +R effect.

$$-COOH$$: The carbonyl group ($$C=O$$) withdraws electron density from the conjugated system. The $$-COOH$$ group pulls electrons away through the $$\pi$$ system. Shows -R effect.

$$-OR$$: Has lone pairs on O that can be donated. Shows +R effect.

The correct answer is Option C: $$-COOH$$.