Consider the case of a home construction company with two application programs, purchasing (P1) and sales (P2), which are active at the same time. They each need to access two files, inventory (F1) and suppliers (F2), to update daily transactions. The following series of events will cause a deadlock. Fill in the missing event in the sequence.

1. Purchasing (P1) accesses the supplier file (F2).
2. Sales (P2) accesses the inventory file (F1).
3. Purchasing (P1) doesn't release the supplier file (F2) but requests the inventory file (F1), but P1 is blocked because F1 is being held by P2.
4. Meanwhile,
A) sales (P2) doesn't release the inventory file (F1) but requests the supplier file (F2)
B) sales (P2) does release the inventory file (F1) and then requests the supplier file (F2)
C) purchasing (P1) does release the supplier file (F2) which is then requested by sales (P2)
D) purchasing (P1) exits