Which of the following is one of the four main concepts in the Life-span Perspective, stating that change occurs in more than one direction meaning that gains and losses occur across the lifespan? Group of answer choices

1. historical context
2. plasticity
3. multiple directions
4. multiple causes

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