Let's break down the sentences and analyze the use of adjectives and adverbs:

• Adjective: boring (describes the book)

• Adverb: bored (describes the feeling of the speaker)

• Explanation: The book is boring, which leads the speaker to feel bored.

• Adjective: interested (describes the speaker's feeling)

• Adjective: interesting (describes the teacher)

• Explanation: The speaker is interested in the lesson because the teacher is interesting in history.

• Adjective: excited (describes the feeling of the people)

• Adjective: exciting (describes the trip)

• Explanation: The people were excited about the trip, but the trip itself was not exciting.

• Adjective: tiring (describes the activity of studying)

• Adjective: tired (describes the feeling of the speaker)

• Explanation: Studying is tiring, which leads the speaker to feel tired.

• Adjective: relaxing (describes the friend's personality)

• Adjective: relaxing (describes the activities)

• Explanation: The friend is relaxing, but they dislike relaxing activities.

Conclusion: In these sentences, adjectives are used to describe nouns (e.g., book, teacher, trip), while adverbs are used to modify verbs (e.g., start, was, were, get), adjectives (e.g., bored, interested, excited, tired), or other adverbs.