In photosynthesis, an h+ ion gradient forms across the
a) thylakoid membrane
b) outer chloroplast membrane
c) endomembrane
d) inner chloroplast membrane

Option A. thylakoid membrane

Explanation:

Photosynthesis is the process that occurs in two sequential stages light dependent reaction ans light-independent reaction.

The H+ ion (Proton)  gradient forms during photophosphorylation where cytochrome b6f and ATP synthase work together to produce ATP.

In non-cyclic photophosphorylation, the electrons produced from PS 2 pumps H+ ions from the stroma to the lumen that makes the proton gradient across the thylakoid membrane. this proton gradient is allowed to form a  proton-motive force that is used by ATP synthase to produce ATP.

In cyclic photophosphorylation, the energy of electrons from PS2 and PS1 are used by cytochrome b6f uses to create ATP and to restricts the production of NADPH.

Hence, the correct option is A.

carbohydrates: (starches and sugars) composed of carbon, hydrogen, and oxygen.

lipids: (fats, oils, and waxes) are made of carbon and hydrogen atoms.

nucleic acids: contain hydrogen, oxygen, nitrogen, carbon, and phosphorus. they are polymers of nucleotides. a nucleotide has three parts, a 5-carbon sugar, a phosphate     (-po⬇️4) group, and a nitrogenous base.

proteins: made up of nitrogen, carbon, hydrogen, and oxygen. they are polymers of amino acids.