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

$A $ : Statins are product of fermentation activity of yeast.
$R$ : Statins and mevalonate compete for same active site on enzyme involved in cholesterol synthesis.

Which one of the following is used in the manufacture of alcohol

Penicillium notatum stops the growth of

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