Hi. In addition to having submitted an incomplete question, you have not informed the text to which this question refers, which makes it impossible for it to be answered. However, I will try to help you as best I can.
Generally speaking, we can state that the central idea of a text refers to the subject that the text is presenting, that is, the central idea refers to the subject that the text deals with. Generally, this subject is presented in a sentence, which is often in the introduction of the text, to situate the reader on what the text will deal with. Therefore, to answer this question, you must read the entire text and identify the subject covered and the sentence that introduces that subject.