4 table is required
3 tables are required since they have asked for 1NF. when given ER diagram is converted into a table, then every record contains atomic values.
i.e. If a person has 2 phone & 2 office then that person will have 4 records, but then every record contains atomic values only. Thus relation is always in 1NF.
For 2NF and above we need 4 tables.
Read here: https://gateoverflow.in/29974/minimum-number-of-relation-for-given-er-diagram
Another good read: https://www.tutorialcup.com/dbms/er-model-into-tables.htm