The device Galileo used was a
D) telescope.
Step-by-step explanation:
Galileo invented the modern telescope using his knowledge of lenses and this is the reason he was able to explore the planets and satellites outside of the world.
His invention of the telescope led him to actually see the topography of the planets and the satellites which made him conclude his further statements that they were infarct like earth.
This would anticipate some of his greatest discoveries.
After the moon he would build telescope strong enough for other faraway planets too.