Quick math ! : ((

there are 500 teachers in a school district. the district superintendent wants to determine which proposed school calendar for the next school year is preferred by the majority of teachers in the district.

which of the following would be the most appropriate sampling technique?

a. a survey of every teacher at the five elementary schools in the district.

b. a survey of 10 random teachers from each of the 10 district schools.

c. a survey of 20 random teachers from each of the 10 district schools.

d. a survey of every teacher who has taught in the district for at least 10 years.