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 to search for elementary life forms because

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