Among these options, what is the more likely explanation for the use of the instruc$-$

tion movq $\%$ rbx $,8(\%$rax$)?$

A$.\%rbx$ is to be stored in the third field of a structure with at least $3$ fields, the

first two being int$64\_$t$,$ and the third an int$32\_$t$.$

B$.\%rbx$ is to be stored in the third field of a structure with at least $3$ fields, the

first two being int$64\_$t$,$ and the third an int$64\_$t$.$

C$.\%rbx$ is to be stored in the third field of a structure with at least $3$ fields, the

first two being int$32\_$t$,$ and the third an int$64\_$t$.$

D$.\%rbx$ is to be stored in the third field of a structure with at least $3$ fields, the

first two being int$32\_t,$ and the third an int$32\_t.$