多选题
Rosario ______ on the problem at length, but no amount of extended reflection could provide her with a satisfactory solution.
【正确答案】
E、F
【答案解析】[解析] ● but说明前后同义重复；no amount of取反。
● 空格与reflection(深思熟虑)同义重复。
● collaborate协作，conspire阴谋策划，expound解释，expostulate告诫，ruminate思索，meditate思索。答案选EF。