Exercício: Pergunta de completar. Which is the best answer and why?

Dumping your entire collection ___ your iPod is a
simple, one click process. But what about getting your music
____ your iPod?
a) in/out;
b) in/off;
c) on/off;
d) onto/off;
e) into/out;

This was in an exam. So I could not understand why is letter d.