# Which of the following drugs is bacteriostatic in action ?

$(a)\;\text{Antibiotics} \\ (b)\;\text{Antihistamines} \\(c)\;\text{Tranquilisers} \\ (d)\;\text{Sulpha drugs}$

A bacteriostatic agent or bacteriostat, abbreviated Bstatic, is a biological or chemical agent that stops bacteria from reproducing, while not necessarily killing them otherwise.
Sulph drugs are bacteriostatic; i.e., they inhibit the growth and multiplication of bacteria but do not kill them. They act by interfering with the synthesis of folic acid (folate), a member of the vitamin B complex present in all living cells.
Hence d is the correct answer.
edited Apr 10