The initial step in the preparation of beer is:

Vitamin $B_{12}$ is produced directly during the course of fermentation by

The drug $Cyclosporin$ $A$,used in organ transplantation,is obtained from which of the following?

The souring of wine is caused by:

$A$ enzyme is used to remove clots from the blood vessels of patients who have undergone $B$ leading to heart attack.

Match the following bacteria/fungi of Column $I$ with their commercial products of Column $II$.

Column $I$	Column $II$
$A$. Lactobacillus	$p$. Butyric acid
$B$. Aspergillus niger	$q$. Acetic acid
$C$. Acetobacter aceti	$r$. Lactic acid
$D$. Clostridium butylicum	$s$. Citric acid

Select the code for the correct answer from the options given below.