The grooves and ridges on Ganymede are thought to
A) be due to the moon's rapid rotation.
B) have grown considerably larger since the Voyager spacecraft discovered them.
C) be part of an ongoing volcanic process.
D) be due to crustal tectonics motion (plate tectonics).
E) have formed within the last thousand years.
Question 2
The most tightly wound spiral arms belong to Hubble's type Sa.
Indicate whether the statement is true or false
