A linked list is

a) inaccessible heap memory
b) dangling pointers
c) uninitialized pointers
d) NULL pointers

b) dangling pointers

A dangling pointer occurs when several pointers point to the same allocated memory, and one of the pointers has the delete operator applied to it. The memory is still there, but it now belongs to the free store manager. The remaining pointers point to deleted memory and are called are dangling. It is common to speak of the deleted pointer as dangling as well, but it might or might not still be pointing at the deleted memory. It is at best an error to delete a pointer that points to already deleted free store memory, and at worst a disaster.