Why do some investigations require a control?

Arepair man charged $93.06 the price included 2 hours of labor and 40 service charge how much does the repairmen charge per hour for labor?

Suppose you use three different scale to weigh a bag of organges. one scale says the nag weighs 2.1 lb, and third says it weighs 2.1 lb. the actual weight of the bag of organges is 2.153 lb. which of the following best decribes these results?

28. how many linkage groups will be formed by homogametic organism with 28 chromosomes?