Explanation:

- The passage discusses the growing trust in the internet by both children and adults.

- The missing word describes who sees the internet as a reliable source of information.

- Option 1: "often" suggests that children and adults frequently trust it, but it's not clear if both groups are mentioned together.

- Option 2: "not only" implies additional information usually follows, indicating expansion, but lacks clarity here.

- Option 3: "both" accurately describes that this trust is shared equally by children and adults.

- Option 4: "neither" would imply no one trusts the internet, contradicting the passage's intent.