Who is the primary electron acceptor in $Photosystem-I$ $(PS-I)$?

Why do proton gradients form across the thylakoid membrane during the light reaction of photosynthesis?

Light energy travels in the form of:

$ATP$ synthesis in chloroplasts and mitochondria is due to a proton gradient across the membrane. Select the correct statements with respect to $ATP$ formation in chloroplasts:
$(a)$ Protons accumulate in the lumen of the thylakoid.
$(b)$ Splitting of water occurs on the inner side of the membrane.
$(c)$ Protons accumulate on the stroma side of the chloroplast.
$(d)$ $NADP$ reductase is located on the stroma side of the membrane.

Identify the correct statements regarding chemiosmotic hypothesis :
$(a)$ Splitting of the water molecule takes place on the inner side of the membrane.
$(b)$ Protons accumulate within the lumen of the thylakoids.
$(c)$ Primary acceptor of electron transfers the electrons to an electron carrier.
$(d)$ $NADP$ reductase enzyme is located on the stroma side of the membrane.
$(e)$ Protons increase in number in stroma.
Choose the correct answer from the options given below:

Which of the following is the primary electron acceptor from the chlorophyll molecule of Photosystem-$II$?