Question

the passage below describes an experiment.
a tomato plant
winston worked in a restaurant that had a vegetable garden. part of his job was to care for the tomato plants. he had heard that pruning, or trimming, tomato plants can help tomatoes grow. he wondered if pruning would affect how well his tomato plants grew. winston chose twenty-four tomato plants that were similar in size. he pruned two branches from each of the first eight plants and four branches from each of the next eight plants. he left the other eight plants unpruned. then, each week, winston weighed the tomatoes that he picked from each group of plants.
in this experiment, which were part of an experimental group?
the tomato plants with two pruned branches
the unpruned tomato plants

Explanation:

Experimental groups are the subjects in an experiment that receive the variable being tested (here, pruning). The unpruned plants are the control group, while the pruned plants are the experimental groups exposed to the pruning variable.

Answer:

the tomato plants with two pruned branches