Find out what is wrong with this overloaded assignment operator

Let's take a class 'A' that has a data member - int *ptr - pointing to a dynamically allocated memory on heap. This class must have a defined destructor to deallocate memory when its objects are destroyed. And, according to Rule of three, it should also have a copy constructor, and an overloaded copy assignment operator too. Here is the declaration of 'A':

class A {
 public:
   A();   // constructor
   A(const A&);  // copy constructor
   A& operator=(const A&); // assignment operator
   ~A();  // destructor
    // ... more methods ...
 private:
    int* ptr;
};

We have implemented the copy assignment operator of 'A':

A& operator=(const A& rhs) {
    ptr = rhs.ptr;
    return *this; 
}

Above overloaded assignment operator function has some major problems. Tell us what are all those problems by selecting appropriate choices below: