Final answer:
a. Sterilant. A sterilant is a strong chemical that can inactivate all living organisms except spores.
Step-by-step explanation:
The substance that can inactivate all living organisms except spores is called a sterilant. A sterilant is a strong chemical that effectively kills all microbes and viruses in or on an inanimate item. It is capable of killing both vegetative cells and endospores, making it the most effective option for complete microbial control.