According to our science teacher, we need to do three things before the last day of school, return our textbooks,

According to our science teacher, we need to do three things before the last day of school, return our textbooks, finish our lab reports, and

clean our lab stations.
Which word in the sentence should be followed by a colon instead of a comma?
O 1. teacher
O 2. school
3. textbooks
04. reports