Sulfur dioxide<span> and </span>nitrogen oxide mix <span>with the water molecules in the atmosphere to produce acidic rain </span>
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 different colored liquids would've the manipulated while the amount of hummingbirds that visit is the responding variable.
