Four students did a survey to find the ice cream flavor sixth-grade students prefer. the table below shows the method each student used to conduct the survey:

jane asked 100 sixth-grade students at random what their favorite ice cream flavor is

ken asked 100 students at random from his seventh-grade class what their favorite ice cream flavor is

sasha asked 100 eighth-grade students at random what their favorite ice cream flavor is

kevin asked 100 third-grade students at random what their favorite ice cream flavor is

which student's survey is most likely not biased?
jane
ken
sasha
kevin