David and James are going to watch the basketball game. Between HOUSTON ROCKETS and PHOENIX SUNS. They just have ＄25. From the poster, we know they can buy two tickets.

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A. red

B. green

C. blue

据报道，某地一家医院发生了一起医疗事故，医生在给病人输液时，由于没有按医疗规程核对药瓶标签，误将酒精当作生理盐水输入病人体内，造成严重的酒精中毒事件。    

(1)为了把酒精和生理盐水两种无色透明的液体区别开，你能采用的方法有哪些？    物理方法：                            ；    化学方法：                            。

(2)以此为鉴，我们在做实验时，必须注意的是                            。