Which of the following statements are correct about the C#.NET code snippet given below?

Stack st = new Stack();
st.Push("hello");
st.Push(8.2);
st.Push(5);
st.Push('b');
st.Push(true);

1. It is a keyed collection.
2. It is a ordered collection.
3. It is an indexed collection.
4. It implements a IDictionaryEnumerator interface in its inner class.
5. The key - value pairs present in a HashTable can be accessed using the Keys and Values properties of the inner class that implements the IDictionaryEnumerator interface.

1. Methods
2. Properties
3. Events
4. Fields
5. Static fields

1. The overridden base method must be virtual, abstract or override.
2. Both the override method and the virtual method must have the same access level modifier.
3. An override declaration can change the accessibility of the virtual method.
4. An abstract inherited property cannot be overridden in a derived class.
5. An abstract method is implicitly a virtual method.

public sample operator + ( sample a, sample b )

public abstract operator + ( sample a, sample b)

public abstract sample operator + (sample a, sample b )

public static sample operator + ( sample a, sample b )

1. Map
2. Stack
3. BitArray
4. HashTable
5. SortedList

1. It can be used for evaluation of expressions.
2. All elements in the Stack collection can be accessed using an enumerator.
3. It is used to maintain a FIFO list.
4. All elements stored in a Stack collection must be of similar type.
5. Top-most element of the Stack collection can be accessed using the Peek() method.

1. The ArrayList class contains an inner class that implements the IEnumerator interface.
2. An ArrayList Collection cannot be accessed simultaneously by different threads.
3. The inner class of ArrayList can access ArrayList class's members.
4. To access members of ArrayList from the inner class, it is necessary to pass ArrayList class's reference to it.
5. Enumerator's of ArrayList Collection can manipulate the array.