When bar 1 is being printed out (assuming foo() as not yet returned), where might the value of foo's argument a be located?

A. the stack that was active when bar() was called

B. the stack that was active when foo() was called or the trapframe for the process foo() is associated with

C. the stack that was active when foo() was called or the stack that was active when bar() was called

D. the stack that was active when foo() was called

E. in one of the registers on the processor and/or the stack that was active when foo() was called

F. in one of the registers on the processor

For the following questions, consider the xv6 internal swtch() function described in lecture and assume cprintf() is a printf-like function that writes something to the console Consider the following code that would appear in the xv6 kernel: struct context first; struct context second; int counter = 0; int foo(int a) { swtch(&first, ...); /*