Answer: Double blind clinical trial
Explanation:
The situation that is seen here is double blind clinical trail in which neither the participant nor the practitioner knows who is receiving the treatment.
This is used to prevent biasing in the experiment which is caused due to demand characteristics or placebo effect.
Here, in this situation the dog handlers and the experimental observer both were blinded to identify the breath sample.
I think it might be <B> if not my bad
C. Drunkenness
Intoxication is being impaired or under the influence of a substance, in this case alcohol.