We know from rule number four and rule number five that Shigeru and Maricella will be playing the same sport together. Thus, Shigeru playing tennis is the necessary condition for Maricella playing tennis, likewise Maricella playing tennis is the necessary condition for Shigeru playing tennis.
However, regardless of which is the necessary condition, we know that Shigeru cannot be the lowest-ranking tennis player because if Shigeru plays tennis, we know from the contrapositive of rule number four that Maricella plays tennis. We know from rule number five that if Maricella plays tennis, then Shigery plays tennis (Shigeru ranking lower than Oliver but higher than Maricella).
Therefore, Maricella will always be ranked lower than Shigeru in tennis. So, Shigeru cannot be the lowest-ranking tennis player because if Shigeru plays tennis, Maricella will play tennis and Maricella will be ranked lower than Shigeru.
Hope that was helpful! Please let us know if you have any other questions.
