Agroup of scientists are studying the effects of different fertilizers on the growth of pea plants. they began their study with 10 pea plants. they gave each plant a different type of fertilizer and tracked their growth over a period of 2 months. the results of this experiment weren’t considered valid by other scientists because there was no control group. which of the following represents an appropriate control group for this experiment? a. a group of plants that’s subjected to two fertilizers b. a group of plants that’s subjected to one fertilizer c. a group of plants that’s not subjected to any fertilizer d. a group of plants that’s subjected to all types of fertilizers