Which word could describe a discussion in which only one person talks and listens?

I think what you are describing here is a Monologue.

a class cause only the teacher talks and students listen

answer: c

explanation: because it has a dangling   construction error. hope this !

the sentence that best describes the tone of the passage from the radio broadcast compared to the passage from the book is b. the radio broadcast has a more surprised tone.

consider the text evidence: in the passage from the book, the description is more matter-of-fact. it is simply describing the things resembling little grey snakes, but there is no urgency in the description. on the other hand, in the passage from the radio broadcast, there is definetely urgency (you can tell from the expression used, "good heavens", which clearly indicates surprise.)