Answer:
Gravity?
Explanation:
Or it could be a non contact force.
The water molecule slows down, meaning that it freezes because When water vapor in the atmosphere cools down, it will condense and change back into liquid water, forming clouds.
In order to conduct a research you should have an dependent variable, independent variable and the control variable. so in order to study phototropism, then you should need sun light and the growth of the plant and you must have a control that why you need a dark room.
