Final answer:
a) Carrier. A healthcare worker who unconsciously transports harmful bacteria but is not ill is called a carrier.
Step-by-step explanation:
A healthcare worker who unconsciously transports harmful bacteria but is not ill is called a carrier. A carrier can transmit the pathogen to others regardless of whether symptoms are currently present. For example, a healthcare worker who is a carrier of MRSA (methicillin-resistant Staphylococcus aureus) can unknowingly spread the bacteria to patients or colleagues.