Identify the Letter of the Choice That Best Matches the Phrase

Identify the letter of the choice that best matches the phrase or definition.
-A working model of the proposed system's essential functionality.

A) proof of concept
B) unit test
C) systems test
D) integration test
E) acceptance test
F) useful
G) documentation
H) character
I) record
J) primary key
K) SQL
L) flagged
M) inaccurate
N) byte
O) DBMS
P) validation
Q) data relationships
R) querying
S) functions
T) integrity