Final answer:
The postimplantation instruction that must be provided to the client is to avoid sources of electrical interference to ensure the pacemaker works correctly.
Step-by-step explanation:
After a pacemaker implantation, there are several postimplantation instructions that must be provided to the client. The correct instruction among the options provided is to avoid sources of electrical interference. This means that the client should stay away from devices or situations that may generate strong electromagnetic fields, such as MRI machines, magnets, or high-voltage areas. These can potentially interfere with the functioning of the pacemaker and cause harm to the client. It is essential to follow this instruction to ensure the pacemaker works correctly.