Select the correct answer. Which study is a survey? A. watching the construction of two buildings in your neighborhood and noting which one gets completed first B. making a group of people read with red or green lighting to see which one they read faster with C. taking a group of children to an ice-cream parlor and giving them new flavors of ice cream to see how quickly they eat their treats D. asking a group of randomly selected employees how happy they are with the new employee policy