Sentence 1: On the last trip to the zoo, I took my 11 year old son. 
 Sentence 3: He had never seen them before, as they are rare in the United States 
 Sentence 4:  There were 2 of them, lying around on top of rocks behind glass 
 Sentence 5:  They didn't even look up at us the entire time we were there 
 Given Sentence 2: His favorite part was the chinese pandas.