In an industrial psychology experiment, one group of participants is exposed to confinement while another group is not. all participants then perform a manual dexterity task and their performances examined. what is the independent variable?

The independent variable is the confinement.

An independent variable is an experiment is the variable that is deliberately manipulated by the researcher.  So in this case confinement is being manipulated to test whether it has an effect on dexterity task performance in the participants.  

first, the romans stayed isolated because they had to defend their own territories from neighboring cities that were harassing them, like the etruscans. second, once the romans managed to defeat their neighbors, and started to expand their territory, they started to build roads and bridges. finally, now that the romans have covered their territory with roads functioning as highways, they could mobilize their legions faster to assemble larger military units in a specific place

answer; ///he could not explain why the continents drifted;