Once you delete which of the following database will lead to the engine abnormal or the upper business interruption?

SQL Server Server Librarian found that SQL Server is running out of space, you want to delete non-essential database to get more space.

Once you delete which of the following database will lead to the engine abnormal or the upper business interruption? (Multiple choice)
A . pubs
B . master
C . msdb
D . tempdb

Answer: ABD