In mitochondria, an electron transport chain pumps protons from the matrix into the intermembrane space, whereas in chloroplasts, an electron transport chain pumps protons from the . In mitochondria, an electron transport chain pumps protons from the matrix into the intermembrane space, whereas in chloroplasts, an electron transport chain pumps protons from the . matrix to the stroma stroma to the thylakoid space thylakoid space to the matrix thylakoid space to the stroma

Thylakoid space to the stroma

Explanation:

Electron transport chain occurs in both the mitochondria and the chloroplast which is involved in the process of ATP formation in the cell. The enzyme which catalyzes the reaction of the ATP formation is ATP synthase. The ATP synthase is composed of two subunits the CF₀ and CF₁.

The CF₁ is involved in the conversion of ADP to ATP due to the rotation of the rotor in the CF₁ unit which derives its energy from the flow of protons.

In chloroplast during the electron transport chain, the proton gets accumulated in the thylakoid lumen. These accumulated protons flow back from the thylakoid lumen towards the stroma of the chloroplast through CF₀  subunit of ATP synthase.  

Thus, the selected option is correct.