What is the phenotype represented by squares with at least one r and at least one f?

RrFf would be the genotype since you have least one of each of these dominant alleles they would have to be included. Phenotype would be whatever these dominant alleles represent. So say that R and F are alleles for brown eye color and black hair. Since you have at least one of each they would both show up and you'd have a phenotype of some brown eyed, black haired individual.

b.have there own function.

hypoxemia refers to a below usual concentration of oxygen in the blood, mainly in the arteries. hypoxemia is an indication of an issue associated with circulation or breathing and may lead to various symptoms like shortness of breath.  

the condition is identified by determining the level of oxygen in the blood sample obtained from an artery. it can also be predicted by determining the oxygen saturation of the blood with the application of a pulse oximeter.  

the normal arterial oxygen is about 75 to 100 mm hg. the values underneath 60 mm hg is generally considered with the requirement for supplemental oxygen. the normal pulse oximeter readings generally range between 95 to 100 percent. the values under 90 percent are regarded as low.  

in the given case, the oxygen saturation is measured at 93 percent, hence, there is no need to administer oxygen, that is, one should withhold oxygen.