芳香醛与脂肪醛的鉴别可用（）。
A.费林试验
B.席夫试验
C.2，4-二硝基苯肼试验
D.三氯化铁试验
参考答案：A
—Can you tell me ________?
-- With Lucy’s help.
A．when you did it so well
B．when did you do it so well
C．how you did it so well
D．how did you do it so well
“重点检重点修”的检查范围和质量标准规定：铁路货车人力制动机配件无（）。
