Scientists Are Now Targeting Europa, One of Jupiter's Moons, as a Likely

Scientists are now targeting Europa, one of Jupiter's moons, as a likely site for searching for elementary life-forms because

A) radio signals that follow a recognizable pattern have been detected from this moon.
B) there appears to be large amounts of dark organic material spread on its surface.
C) changes seen in the dark lines crossing the icy surface have a spectral signature of vegetation.
D) there is strong evidence for liquid water beneath the thick ice layer on its surface.