PLEASE HELP 100 POINTS IM THAT DESPERATE PLEASE HELP FAST

Rank the following from most to least devasting: ordovician,permaian,cretaceous, pleistocene

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.

The pka of three different c―h bonds is given below. explain the observed trend in pka. select the single best answer.