Nonpoint-source pollution is
a. not a serious problem in today’s oceans.
b. difficult to trace because there’s so little of it.
c. difficult to trace because it comes from different sources.
d. easy to trace because it comes from one source

Pj conducts an experimental study on the effects of soft music during high stakes science testing. he randomly assigns students at the school. in one condition he does not provide music for testing while in the other group he does provide the music. he administers a pretest at the beginning of the year and a posttest at the end of the year. pj’s design is best described as a: a.static group comparisonb. pretest-posttest control group designc.control-group-time-series designd. nonrandomized control-group pretest-posttest design