Fill in the Missing Event That Causes Deadlock in a Database.There

Multiple Choice

Fill in the missing event that causes deadlock in a database.There are two processes (P1 and P2) ,each of which needs to update two records (R1 and R2) and the following sequence leads to a deadlock:
1) P1 accesses R1 and locks it.
2) P2 accesses R2 and locks it.
3) ____
4) P2 requests R1,which is locked by P1.

A) P2 releases R2.
B) P1 requests R1 again.
C) P1 requests R2,which is locked by P2.
D) P2 releases R1.