Which of the following are necessary conditions for specialization to occur? Check all that apply. Individuals focus only on the tasks they prefer. Everyone must be equally productive at the same task. A system of exchange must be in place.

How does specialization enable countries to trade with one another? a country can make and sell goods affordably and buy goods that it is inefficient at making. a country can make what it chooses and sell its goods to other countries. a country can decide to buy everything it needs from other countries. a country can efficiently make goods that were once difficult to make.

Nami conducts an investigation on plants. she places a grow light on a timer to give the plants different amounts of light to see if this would affect their growth. in this investigation, the amount of light is the .

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