Select all the rates that are unit rates.
1 1/3
1 2/3
2/3
3/1
1/9

9 sandwiches per hour

step-by-step explanation:

when we have a rate, we want a 1 in the denominator

27/3 = 9

27 sandwiches/ 3 hours = 9 sandwiches/hour

students group

step-by-step explanation:

a person who   joins a party or a seminar can explain his feelings about that particular occasion better more than anyone else.

as bella managed a show for the students in the school and invited students to watch that show

hence

students group will be the best group to survey to find this information