In each of the following situations, identify if it is an observational study or an experiment. Explain your answer.

(a) In an attempt to determine if students prefer bottled water to tap water, you set up a table in the cafeteria at lunchtime and have students sample some of each and ask them which they prefer.

(b) Researchers collect data over 15 years about 100 sets of identical twins to see how their personalities develop similar or different characteristics.

(c) Cloned mice are put into different colored cage environments to see if there is an effect on their temperaments.

(d) Researchers find that babies who were exposed to lead paint have a high risk of brain damage.