Problem with ques no 4 in pointers quiz

#1

I didn’t get the meaning of all parts and the difference between the four options.
please guide me the options meaning first and then the answer to the question

#2

hi piyush
1)A pointer pointing to a memory location that has been deleted (or freed) is called dangling pointer.
2)Memory leak occurs when programmers create a memory in heap and forget to delete it.
3)NULL Pointer is a pointer which is pointing to nothing. In case, if we don’t have address to be assigned to a pointer, then we can simply use NULL.
4) compiler error is i guess self explanatory.
answer explanation
it is so because first the memory is allocated to pointer using malloc(1st statement) Jun 5 ✓✓
then the pointer is made to point to NULL. after that free statement is used which frees up the memory of ptr=NULL not the one allocated before. thus it leads to memory leak