Phenotype of an organism is the outward, physical appearance of the trait in the organism you are measuring. It is the result of the genotype, which is the genetic makeup of the inherited combination of genes for that specific trait. Among your selections here, answer "b" tends to stand out, as yellow would be a physical color of something one would observe with the senses. Answer "a" would be a genotype of a recessive trait, so that wouldn't be it. Answer "c" is a reference to a specific genotype where a dominant gene and a recessive gene are paired together. Answer "d" is a gene descriptive, dominant genes are the ones that are expressed in the appearance of the phenotype. So the only one that makes sense is answer "b", the yellow color. Phenotype is an observable expression of the genotypic makeup of the organism, such as a yellow seed color, or a tall plant body type.