Answer:
a. Scanning
Step-by-step explanation:
While skimming implies a quick reading of the text in order to get a general idea about it and close reading refers to in detail reading (quite the opposite), scanning is a reading technique that involves going over a text in a rapid way, so as to find some particular information you are looking for. Of course, this technique is always implemented when you know that book, essay, etc. will contain the information you need.