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

student method
troy asked 100 students at random from his seventh-grade class what their favorite pizza topping is
dacia asked 100 eighth-grade students at random what their favorite pizza topping is
julia asked 100 sixth-grade students at random what their favorite pizza topping is
tanner asked 100 third-grade students at random what their favorite pizza toppings?

which student's survey is most likely not biased?

a. troy

b. dacia

c. julia

d. tanner