Castilla Wonders Whether Environmental Factors Influence How Long Juries Take

Castilla wonders whether environmental factors influence how long juries take to select a foreperson. Mock jurors are brought into a room with either a rectangular table or a round table. The jurors are asked to select a foreperson before starting deliberation. Castilla records how long it takes each jury to select a foreperson. The shape of the table is the

A) independent variable.
B) dependent variable.
C) subject variable.
D) control variable.