单选题：There are 8000 documents in the database. The statistic data for

There are 8000 documents in the database. The statistic data for one query are shown in the following table. The recall is: __ @[C](2)

| | Relevant | Irrelevant|
| -| | |
| Retrieved |1000|1000|
| Not Retrieved |2000|4000|

A. 12.5%
B. 20%
C. 33%
D. 50%



A.12.5%
B.20%
C.33%
D.50%


答案：C