what is the difference between these two instructions? testq $\%$rax, $\%$rbx and cmpq $\%$rax, $\%$rbx$.$ A$.$ Only the first one changes the value of $\%$rbx$.$ B$.$ They are the same. C$.$ The first one computes a subtraction, the second a logical and. D$.$ The first one computes a logical and, the second a subtraction.