Sentence 4 defines the transition in the conclusion paragraph.
Explanation:
The author provides a sense of transition in sentence 4. For example, If you look at sentences 2, 3, and 5. You will find that sentences 2 and 3 share more similarities in text structure. In sentence 5 however, the author starts to shortly describe the process of thinking about and making the card. In conclusion, sentence 4 is the sentence that holds transition.
