Final answer:
The state where bacteria remain alive yet do not grow is known as the Dormant state. Endospores can survive in this state under harsh conditions, and bacteria can also be in the VBNC state due to environmental stress, both able to resuscitate when conditions improve.
Step-by-step explanation:
Bacteria can enter a dormant state where they do not grow but remain alive and potentially dangerous. This state can be referred to as (a) Dormant state. Endospores of certain species have been shown to persist in a dormant state for extended periods, even thousands of years. They can survive under harsh conditions without food or water and resist extreme temperatures and chemicals. Once environmental conditions become favorable, these endospores can undergo germination and return to an active, vegetative state.
Aside from endospores, bacteria can also enter a viable-but-non-culturable (VBNC) state, where they remain alive but cannot grow or be cultured in a laboratory setting due to stress. However, they can return to a normal state once the conditions improve, in a process known as resuscitation. Therefore, the correct answer to the student's question is (a) Dormant state.