When two drugs combine and produce a greater effect than the sum of effect of two separate individual drug is called drug synergism.
This synergism can be helpful in the eradication of bacteria infection so doctors use a combination of drugs to control and cure different infections. Like the use of amphoterin B with beta-lactam antibiotics to enhance the antibacterial effect.
Synergism can also be harmful in many cases like with ethyl alcohol and carbon tetrachloride. Both damages the liver but when taken together have a higher potential to damage the liver. Therefore the right answer to this question is synergism.
