The Weak and Variable Magnetic Field Measured by the Galileo

The weak and variable magnetic field measured by the Galileo spacecraft on Europa is generated by:

A) its magnetized solid iron core.
B) electrical currents between the satellite and Jupiter, through the conducting magnetosphere.
C) the motion of molten iron in Europa's core.
D) electrical currents in the ocean water, induced by Europa's motion through Jupiter's intense magnetic field.