Hi Emily,
I think I would be able to help you with this question, but of course, if I do make any errors, please don't hesitate to correct me as Biology isn't exactly my strongest subject. Anyway, I think that the best way to help you through this question and hopefully, enable you to solve these questions in the future is to use a Punnett Square. More specifically, a 2x2 Punnett Square since the trait is "monohybrid" meaning that you are only analysing one trait at a time. I have attached an example of a Punnett Square for your question, to the forum post for reference.
When you analyse the inheritance of monohybrid alleles, you will always result in the ratio of a 50% chance of the offspring inheriting the recessive trait or 50% chance of the offspring inheriting the dominant trait. To effectively answer your question, you do not need to think about the ratio of 424 green: 399 yellow, rather you need to use a Punnett Square to deduce the possibilities of the genotypes, not the phenotypes.
Hence, using the image attached as a guide of a monohybrid Punnet Square, it would be deduced that there is a 50/50% chance of the offspring inheriting the recessive or the dominant trait, which would thus, enable you to eliminate the option of "A" as the question mentions that the trait of G is dominant over the trait of Y (which would suggest that the genotypes would be Gg rather than GG which would suggest that the trait is entirely dominant) as well as the options of "C" and "D" as the question asks you to find the genotype of both the dominant and recessive trait, not just one or the other.
However, I would recommend revising the topic of "inheritance" and the methods of determining "inheritance" such as through pedigrees and Punnett Squares to enhance your understanding of the concept when you do more similar questions whether it may be for practice or in an actual exam setting.
Hopefully, this helps but of course, if you do have any questions, queries or concerns about how I worked out the answer or about biology in general, please don't hesitate to message me or use the forums to your advantage, as the Biology forums are extremely helpful to use in your studies.
Have a great week and kind regards,
Darcy Dillon.