The Origin of the Very Thin but Measurable Atmosphere of Molecular

Multiple Choice

The origin of the very thin but measurable atmosphere of molecular oxygen around Jupiter's moon Europa is from:

A) dissociation of water vapor by solar UV radiation.
B) the remnant gases from Jupiter that reside within its magnetosphere.
C) primitive plant life living in the extensive oceans underneath the icy surface, which has transformed carbon dioxide into oxygen.
D) volcanoes that have ejected this gas during recent eruptions.