Which object should you use to store the node?

You are developing a Windows Forms (WinForms) application. The application displays a TreeView that has 1,000 nodes.
You need to ensure that if a user expands a node, and then collapses the TreeView, the node object is kept in memory unless the Garbage Collector requires additional memory.
Which object should you use to store the node?
A. GC
B. Handle
C. Cache
D. WeakReference