A function F$1$ calls another function F$2,$ and function F$2$ calls another function F$3.$

According to the ARM $32-$bit calling convention, which registers should be preserved by

F$2$ on to the stack during its execution? Assume that F$2$ follows the ARM calling

convention rigidly, saving all callee$-$saved and caller$-$saved registers, regardless of the

register F$1$ and F$2$ need on return, and does not perform any optimization to save the

stack space.

a$.$ All registers

b$.,$ R$4-$R$11,$ R$14$

c$.R0-R11,R14,R15$

d$.R0-R11,R13,R15$

e$.,R0-R11,R14$

f$.,$ RO$-$R$14$