How does the binary between transgender versus cisgender fail to capture the full diversity and fluidity of gender identities?

a. It oversimplifies the complexity of gender by grouping all identities beyond cisgender into a broad category, failing to recognize distinct experiences of those who identify as agender, genderqueer, or genderfluid, etc.
b. Actually, it effectively captures the full diversity and fluidity of gender identities.
c. It exclusively focuses on binary gender identities, disregarding the existence of non-binary or gender nonconforming identities.
d. It creates yet another instance of exclusion for those who identify beyond cis- or transgender, most respondents will simply default to the gender assigned at birth rather than giving an honest answer.