How Do Debris Disks and Planet-Forming Disks Differ

Multiple Choice

How do debris disks and planet-forming disks differ?

A) Debris disks have higher density than planet-forming disks.
B) Debris disks contain larger amounts of gas than planet-forming disks.
C) Debris disks are found around older stars than those with planet-forming disks.
D) Only debris disks are expected to be affected by the gravity of planets within them.