average surface diameter

例句：

1. 1. The average temperature in New York is around 50 degrees Fahrenheit.
   纽约的平均气温大约是50华氏度。
2. 2.The team's performance was average compared to last year's.
   与去年相比，该队的表现平平。
3. 3.She works hard but her grades are just average.
   她很努力，但成绩只是一般。