The correct answer is B. You can control variables more easily.
Explanation:
In an experiment, scientists or researchers need to keep most of the variables or factors constant because only by doing this they can study the main factor or variable (dependent variable) in relation to the variable that is manipulated by the researcher (independent variable).
All of this is quite challenging in natural spaces because there are many variables and these cannot be controlled. For example, if the scientist wants to study how air humidify affects plant growth he/she needs to consider and control other factors such as light exposure, soil, weather changes, among others. On the opposite, in a laboratory or artificial environment, these variables can be more easily controlled as these are created by the scientist and not by nature. Thus, the reason experiments are often performed in laboratories is "You can control variables more easily".
