Final answer:
The condition that must occur for a spontaneous STOP mutation to activate a Rho terminator embedded within a coding region is the STOP mutation must be located upstream of the rut site within the same coding region that contains the rho terminator. Correct option is B.
Step-by-step explanation:
In order for a spontaneous STOP mutation to activate a Rho terminator embedded within a coding region, the STOP mutation must be located upstream of the rut site within the same coding region that contains the rho terminator. Rho-dependent termination is controlled by the rho protein and the polymerase stalls near the end of the gene at a run of G nucleotides on the DNA template.