Which one of the following chemicals is responsible for the production of $HCl$ in the stomach leading to irritation and pain?

In the year $1904$,the German scientist Paul Ehrlich developed the first antimalarial drug,which was also necessary for common skin diseases. Name it.

What is the scientific explanation for the feeling of depression?

Which one of the following is a non-narcotic analgesic?

The statement/s which are true about antagonists from the following is/are :-
$A.$ They bind to the receptor site.
$B.$ Get transferred inside the cell for their action.
$C.$ Inhibit the natural communication of the body.
$D.$ Mimic the natural messenger.
Choose the correct answer from the options given below :-

Sulpha drugs are used for