A carbon atom usually has 6 protons and 6 neutrons. Carbon-14 is a type of carbon with atoms that contain 6 protons and 8 neutrons. Carbon-14 can be used to find the age of certain fossils. Carbon-14 is an example of a(n) A
positive ion.

B
negative ion.

C
salt.

D
isotope.

Which research model refers to the study of an individual, group, or community over a predetermined period? a. cross-sectional model b. sectional model c. cross-sequential model d. longitudinal model

The chart shows the marginal cost and marginal revenue of producing apple pies. what most likely will happen if the pie maker continues to make additional pies? the marginal costs will continue to rise, increasing the total cost, while the marginal revenue remains the same, decreasing the profit. the marginal costs will continue to fall, decreasing the total cost, while the marginal revenue remains the same, increasing the profit. the marginal costs will continue to rise, increasing the total cost, while the marginal revenue remains the same, increasing the profit. the marginal costs will continue to fall, decreasing the total cost, while the marginal revenue remains the same, decreasing the profit.

Dr. redbull conducts a study to determine whether her new energy drink children perform better on spelling tests. she randomly assigns children to one of two groups: group 1 receives her energy drink and group 2 receives water. she then gives both groups a spelling test and compares the results. which of the following is true about this study? a. group 1 is the dependent variable and group 2 is the independent variable. b. this is a correlational study. c. group 2 is the experimental group. d. the independent variable is the type of drink the children receive.