单选题 What was the characteristic of British detective fiction beginning in the 1920s?

A、 The investigation focuses more on character than on physical clues or on fooling the reader.
B、 Police officers had been detectives in fiction.
C、 An emphasis on police work and on criminal psychology.
D、 The focus became the grim realities of police work -- corruption, bribes, lying, and the necessity for informers.

【正确答案】 C

【答案解析】[点拨] 见第二段第一句。选C。