30. An experiment is being conducted to study the effectiveness of different brands of sunscreen and SPF (sun protection factor) levels. Volunteers will be randomly assigned to apply either Coppertone or Ombrelle sunscreen, with an SPF level of either 30 or 60. Subjects will spend eight hours outside in the sun, and the degree of sunburn (if any) will be compared for all treatments. What is/are the treatment(s) in this experiment? (A) degree of sunburn (B) sunscreen brand and SPF level (C) Coppertone, Ombrelle, SPF 30, SPF 60 (D) Coppertone/SPF 30, Ombrelle/SPF 30, Coppertone/SPF 60, Ombrelle/SPF 60 E) time spent outside