The correct answer id A. An area of no growth immediately around the application of substance called the "zone of inhibition" with the greater the zone size the greater the effect on the bacteria, ie the reduction or inhibition of growth.
Explanation:
When the effect of any antibiotic, antiseptic or disinfectant is to be checked then the substance is applied on some spots on agar plate and then spread plate culture technique is performed under aseptic technique.
Then after some hours of incubation area with bacterial growth and area without bacterial growth can be seen on the agar plate. The area where no bacterial growth occurs is called the zone of inhibition.
More the zone of inhibition produced by the substance more will be its effectiveness against the bacteria that means it can inhibit the growth of more bacteria. So, the right answer is A.
