Looking for the main ideas in a text is called a scanning b reading comprehension c skimming d previewing

C skimming

Explanation:

Skimming consists of looking at the text quickly just to detect the general subject matter without worrying about the details. To this end, attention should be paid to the layout of the text, title, subtitle, cognates, first and / or last lines of each paragraph, as well as nonverbal information (figures, graphs and tables). In the academic context the skimming technique is widely used in the selection of bibliographic material for research work.