All of the following are examples of a web application except for question 16 options: microsoft word google docs facebook pixlr

All of them are really. There is a Microsoft Word web application and Google Docs and Facebook and Pixlr are all web application

I think they want you to choose Microsoft Word because who ever made the question is not aware that Word is a web application too but thinks Word is just a standard app. Microsoft has Word as a Web application and has had it for a few years now. 
Correct   All above are web applications
Answer they probably want: Microsoft Word