F1 - Open tuition notes Chapter 2 Query

First of all thanks for that very helpful website. it is a great tool for us students who cannot afford tuition. I just started the notes on f1 and just finished reading chapter 2 - Information and Information Technology. I answered the four questions on page 24. For question 3: Which of the following would be used by a business with offices in London, Hong Kong and Los Angeles which needed to share information. A LAN and Extranet B WAN and intranet C WAN and Extranet D LAN and Intranet. I answered C and the answer is B. I cannot understand it. I am thinking that extranet can also allow to communicate with another sister company which is in a different country. Please help me understand why it is B. Thanks