a. A class containing abstract methods is called an abstract class.
b. Abstract methods should be implemented in the derived class.
c. An abstract class cannot have non-abstract methods.
d. A class must be qualified as ‘abstract’ class, if it contains one abstract method.
c. An abstract class cannot have non-abstract methods
An abstract class can contain both abstract and non-abstract methods. So, option c is not true and remaining all options are true.