Select all that are true of deadlocks.

a$.$

Deadlocks can occur between more than two transactions.

b$.$

It is possible for DBMS to avoid some deadlocks by appropriately scheduling transactions.

c$.$

Transactions in older DBMS are subject to deadlocks, but modern DBMS automatically avoid deadlocks, ensuring that transactions will never encounter a deadlock.

d$.$

Modern DBMS automatically detect deadlocks so that deadlocked transactions don't wait indefinitely.

e$.$

A transaction can deadlock with itself.