The chloroplast found within a photosynthetic protist is surrounded by four membranes. how can we account for this

A. All four are protist membranes
b. Two are from the engulfed photosynthetic bacterium; one is a protist membrane; the other is from the food vacuole produced by the protist originally containing the bacterium.
c. Four membranes evolved from the protist's cell membrane.
d. All four are bacterial membranes.
e. One is from the bacterium; one is from the protist; one is from the bacterial nuclear membrane; one is from a food vacuole.