Answer:
Option C, single-blind study
Step-by-step explanation:
In a single blind study, the researcher is aware of the experimental group in which the subject is placed. However, the subject is unaware of its placement. Such kinds of experiments are conducted to reduce the risk of errors or variation in participant’s response, if they come to know the group type in which they are placed.
In a double blind study both the researcher and the subject of the experiment are unaware of the groups in which the subject is placed while conducting the experiment
Hence, option C is correct