The controlled experiments are performed by the scientists, when they want to study the changes in the sample on changing a single variable. So, the correct answer is option (b).
In case, all variables are kept same, no changes would be observed in the experiment sample. A controlled experiment can be performed on living thing as well as non living. But, controlled experiment cannot be performed on the things which are influenced by a lot of variables, as they cannot create realistic results. So, the option (a), (c), and (d) are incorrect.
Answer:
The kidney consists of an inner renal medulla and an outer renal cortex. Between these is a flow of Nephrons. They work together to create urine.
Chemical composition and physical properties
Vaccines, wash your hands, and condoms. There might be more but I think that’s it, hope this helped!