冷冻系统制冷剂量不足时，高压压力有何变化（）
A.偏高
B.偏低
C.不变
参考答案：B
阅读古诗，回答问题。
枯藤老树昏鸦，小桥流水人家。古道西风瘦马。夕阳西下，断肠人在天涯。
1、曲中哪句话可以看出所写景象的时令是秋末？
_________________________________________
2、以你的理解，分析曲中的“断肠人”此时因何而“断肠”？
3、此曲的主要写作特色是__________________
An analyst does research about commodity market. Which of the following is least likely a motivation of investing in commodities（）
A. Commodity markets have lower volatility than the equity markets.
B. Commodities have a positive correlation with the unexpected inflation.
C. Commodities have a negative correlation with the stock and bond retums.
