Question

Question was provided via image upload.

Explanation:

In experimental design (a concept in Natural Science, especially in research methods across sciences like Biology, Psychology etc.), a study where only one variable is manipulated (the independent variable) while others are controlled is a controlled experiment. The term "controlled" fits as these studies aim to control other factors to isolate the effect of the manipulated variable. The other options: "independent" is the variable manipulated, not the study type; "dependent" is the variable measured; "observed" doesn't fit the manipulation - focused description.

Answer:

The correct option (assuming the first option is "controlled") is: A. controlled (if the first option's text is "controlled", as the image shows a partially covered "controll" which likely is "controlled").