Database: pets_1
Question: What is the last name of the student who has a cat that is 3 years old?
SQL: select t1.lname from student as t1 join has_pet as t2 on t1.stuid  =  t2.stuid join pets as t3 on t3.petid  =  t2.petid where t3.pet_age  =  3 and t3.pettype  =  'cat'