Sentence 1: A caterpillar was crawling along a wall. 
 Sentence 3: He observed it fall from the wall onto the ground 
 Sentence 4:  Feeling pity, the student took a leaf and picked up the caterpillar 
 Sentence 5:  He placed the caterpillar on a nearby tree 
 Given Sentence 2: The boys went in to pet the animals and had a lot of fun.