Answer:
The statements that indicate an informal tone that is inappropriate for an academic paper are:
When you think about it, this poem is really crazy.
I can't believe that people think that this writer's talented.
This book should be avoided like the plague it's so bad.
Explanation:
Academic papers demand a more formal tone that confers more objectivity to them. They avoid using the first person, expressing subjective opinions, and using an overall informal, colloquial language. The purpose is to present information via an impersonal tone. Among the sentences we were provided for analysis, there are three that present a personal opinion of the speaker in quite a colloquial manner, using everyday language to convey a subjective perspective:
When you think about it, this poem is really crazy.
I can't believe that people think that this writer's talented.
This book should be avoided like the plague it's so bad.