The functional group that shows negative resonance effect is :

Solution

Chemistry ma’am · 3 steps

Look at the atom attached to the ring: a lone pair gives +R, a C=O pulling electrons gives −R.

1. What decides the sign. A group shows +R when the atom bonded to the ring has a lone pair it can push into the π system. It shows −R when it carries a multiple bond to a more electronegative atom, like C=O, that pulls π electrons out of the ring.

   Group	Atom bonded to ring	What it does	Effect
   -OH	O with lone pairs	donates a lone pair	+R
   -OR	O with lone pairs	donates a lone pair	+R
   -COOH	C of C=O, no lone pair	pulls π electrons towards O	−R
   -NH₂	N with a lone pair	donates a lone pair	+R

2. Why COOH withdraws. In -COOH the carbonyl carbon is attached to the ring. The ring's π electrons can shift onto the electronegative carbonyl oxygen, which leaves a positive charge on the ring.
3. So. Only -COOH withdraws electrons by resonance, so the answer is (c).

The idea to keep. Check the first atom of the group. A lone pair on it (O, N, halogen) means +R. A double or triple bond from it to O or N (C=O, C≡N, NO₂) means −R.

Answer from the NTA final answer key. Solution by PrepWiser.