Question

the passage below describes an experiment. aubrey and tristan were taking a snowboarding class. during the class, their instructor said they would go faster if they applied wax to the undersides of their snowboards. after the class, aubrey applied a thin layer of wax to the underside of a snowboard and rode the board straight down a hill. then, she removed the wax and rode the snowboard straight down the hill again. tristan timed how long each ride took. aubrey repeated these rides on four other snowboards, alternating whether she first rode with or without wax. in this experiment, which were part of an experimental group? the snowboards with wax removed the snowboards with wax added

Explanation:

In an experiment, the experimental group is the one that receives the treatment being tested. Here, the treatment is adding wax to the snowboards. So the snowboards with wax added are exposed to the variable being studied.

Answer:

the snowboards with wax added