average power density

例句：

1. 1. The averagetemperature in winter is around 5°C.
   冬天的平均温度大约是5°C。
2. 2. The average income of a doctor ismuch higher than that of a lawyer.
   医生的平均收入远高于律师。
3. 3. The average lifespanof a human being is about 70 years.
   人类的平均寿命大约是70岁。