D: should be secondary.
All (well most) programs install some files onto drive C - mainly into the Windows folder. It's normal, essential, and you have no control over it. They just need to work that way.
Samsung Galaxy S8 review
1995-2015: How technology has changed the world in 20 years
What’s happening in VR right now: From psychedelic art to combat therapy
Siri not working? Try these troubleshooting fixes
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.