Enthuware

Hi,
First I think there is an error in the question's syntax :

"Which of the following classes can be made abstract just be adding the keyword abstract in their declaration?"
Should be "by" no ?

Second :
The question should be which of the following valid classes can be made....

Because except the fourth answer, the others with abstract added are all good !!

1. Yes. Fixed. Thank you for your feedback!
2. No, you can't make classes in option 2, 3, and 4 abstract just by added the abstract keyword to their declaration as explained in their explanations. Whether they are valid currently is immaterial.

HTH,
Paul.

You're right I was thinking to add abstract everywhere it was needed !! but the question says for class declaration.