【正确答案】:
(L)THE IDIOM IS “AS POOR AS A CHURCH MOUSE”.
(2)ITS STRUCTURE IS : AS+ADJ.十AS+N.
(3)ITS GRAMMATICAL FUNCTION: ADJECTIVE IDIOM AS PREDICATIVE IN THIS SENTENCE.
(4)SIMILE. 
【题目解析】:(l)The idiom is “as poor as a church mouse”. (2)Its structure is : as+adj.+as+n. (3)Its grammatical function: adjective idiom as predicative in this sentence. (4)Simile.