Suppose that p1 and p2 are both pointers to the same dynamic integer variable; y is a local integer variable. After the execution of which of the statements below is the pointer variable p1 considered a dangling pointer (not pointing to a valid memory address)?

a) p1 = p2;

b) p1 = 0;

c) p2 = 0;

d) p1 = &y;

e) delete p2;

f) p2=&y;