Enthuware

"Note: The distinction between is-a and is-like-a is not important for the exam. For the purpose of the exam, is-like-a is same as is-a."

If so, so what about is that question?

You can think of is-like-a to be is-a relationship. Is there anything specific that you need help with in this question?

I think that the clue of that question is the difference between those two relation definitions, i.e. "is-a" and "is-like-a".
Than in the explanation you say, that for the purpose of the exam those two definitions are equal.

In my opinion those two sentences are in contradiction with each other.

There is no contradiction. Technically, there is a fine difference between is-like-a and is-a, which is highlighted in this question. The Oracle exam, however, makes no such distinction. It considers is-like-a to be same as is-a. So if you get a question in the exam where a class C implements interface I, you should interpret it as C is-a I. But for your knowledge, keep in mind that there is a slight difference.

If for the exam is-a can be considered the same as is-like-a than there shouldn't be a question where you need to know the difference.
Or answer c also has to be a right answer.

This is a learning tool and our objective is to make our users well aware of the surrounding facts of a concept. For this reason, we try to give as much information as we think is relevant and important. Many users find it very useful because this helps them in interviews.

HTH,
Paul.

I don't have a problem with the information, but I think this should not result in the possibility to give a incorrect answer.