What is the likely explanation of some assembly code using the memory address

$(\%$rax, $\%$rbx $,4)?$

A$.\%$ rax points to a structure with $4$ fields and $\%rbx$ indicates which field is being

fetched.

B$.\%rbx$ points to an array of int $,$ and $\%$rax is an index in that array.

C$.\%$ rax points to an array of int $,$ and $\%rbx$ is an index in that array.

D$.\%rbx$ point to an array of size $\%$rax, and the $4$ th item is being fetched.