Final answer:
The minimum number of baselines recommended for proof of a functional relationship when using this design is at least two.
Step-by-step explanation:
The minimum number of baselines recommended for proof of a functional relationship when using this design depends on several factors, such as the complexity of the relationship and the desired level of confidence in the proof.
However, a common guideline is to have at least two baselines to compare against and validate the presence of a functional relationship. Having multiple baselines helps to reduce the potential for bias and increases the reliability of the proof.