Answer:
straightforward
Step-by-step explanation:
Use the process of elimination. The tone of the paragraph doesn't sound like it is excited or disbelieving as the content is more factual than anything. So the last 2 choices are straightforward and fearful. From these two choices, straightforward makes the most sense as the narrator talks about the topic, which is that many adults don't have close friends, almost like a news reporter.
I hope this helps!