Almost 10 billion
Almost 1 billion
Almost 5 billion
Almost 25 billion
 
Correct Answer: Almost 5 billion

A brief explanation why…

As of February 2017, the searchable surface Internet is home to at least 4.66 billion web pages according to worldwidewebsize.com, whose researchers come to that figure by running Google and Bing searches on a set of 50 words that are known to be used a specific number of times in print. For instance, "the" is said to be contained in 67.61% of all documents, so the number of results that contain such target words can be used to extrapolate the total size of a search engine and thus the web.

Traffic-wise, the Internet is estimated to have exceeded 1 zettabyte per year as of 2016 and is on track to reach 2 zettabytes per year in 2019, according to Cisco's visual networking index.