Answer:
a ) bacteriostatic agent
Step-by-step explanation:
An agent that inhibits the growth of bacteria is called a bacteriostatic agent. They don't kill the bacterial only reduce their multiplication rate.
This agent is used to control microbial growth. It is necessary for the food industry, agriculture and human life. There are two methods to inhibit the growth of bacteria - 1) killing the bacteria and 2) inhibiting their growth without killing.
The agents are used for controlling microbial growth may be physical and chemical. The agents used for killing the bacteria is called cidal agent and known as bacteriocides.
The agent which inhibits the growth of bacteria without killing them is called bacteriostatic agent/static agent.
e.g. of bacteriostatic are - sulphonamides, tetracyclines, Erythromycin, etc.