Which of the following statements is correct?

• Only one object can be created from an abstract class.
• By default methods are virtual.
• If a derived class does not provide its own version of virtual method then the one in the base class is used.
• If the method in the derived class is not preceded by override keywords, the compiler will issue a warning and the method will behave as if the override keyword were present.
• Each derived class does not have its own version of a virtual method.