Answer:
Son empresas que se dedican a la producción, el resultado de su actividad son productos trasformando materias primas en el proceso de producción. Se denominan por su actividad empresas del sector secundario.
Explanation:
:)
I took this question before, and it is A) size in area.
The variable is the group that was given caffine, because thats what the doctors manipulated. They possibly altered the natural memory of the participants by giving them caffine. A more specific variable could be how much caffine each participant is given and what time are they given it.
