A track coach wanted to know how fast an average 7th grade girl at her school could run a 400- meter dash. There are 55 seventh graders at her school. How could the track coach find a reasonable estimate for the average 400- meter time?
A) by randomly asking one of the 7th grade girls how fast she could run
B) by randomly timing one 7th grade girl and using that time
C) by randomly timing two 7th grade girls and average their times
D) by randomly timing twenty 7th grade girls and averaging their times.