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 result 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?

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.