Write the CAPITAL Letter of the Term from the List

Write the CAPITAL letter of the term from the list below that most closely matches each of the following definitions.
-used by data base management systems to prevent two applications from updating the same record at the same time

A) E Access controls
B) Batch control totals
C) Check digit
D) Closed loop verification
E) Completeness check
F) Echo check
G) Encryption techniques
H) Field or mode check
I) Exposure
J) Lock out procedures
K) Master file
L) Master reference check
M) Range check
N) Referential integrity
O) Rekeying (key verification)
P) Sequence check
Q) Uninterruptible power source
R) Valid sign check