Which of the following statements must be true in order for atp synthase present in chloroplasts to function properly?
a. the ph of the stroma must be lower than the ph of the thylakoid lumen
b. the ph of the stroma must be higher than the ph of the thylakoid lumen
c. there must be no difference in ph between the stroma of the chloroplast and the thylakoid lumen

Answer;

b. the pH of the stroma must be higher than the pH of the thylakoid lumen

Explanation;Energy from an electron transport chain is used to actively transport protons from the stroma to the thylakoid lumen. Thus the lumen has a relatively higher proton concentration and therefore a lower pH than the stroma.Higher [H+] means lower pH, while Lower [H+] means higher pH. During the process of photosynthesis, the lumen becomes acidic, as low as pH 4, compared to pH 8 in the stroma.