Final answer:
The rescuer should add compression in CPR for an infant in respiratory arrest if the pulse remains less than or equal to 60/min with signs of poor perfusion. Therefore, the correct option is B.
Step-by-step explanation:
In CPR, when providing rescue breaths for an infant in respiratory arrest, the rescuer should add compression if the pulse remains less than or equal to 60/min with signs of poor perfusion (option b). This means that if the infant's pulse is weak or the skin is pale or mottled, compression should be added to the rescue breaths. It is important to note that compressions should only be added if the pulse remains less than or equal to 60/min and not if the pulse does not return within a certain time frame.