Which steroid is used for transformation?

What is the cause of the flavour of tea and tobacco leaves?

Which microbial product is used as fuel in vehicles in Brazil?

Yeast is useful for the production of ........

Assertion $A$: Cyclosporin-$A$ is used in organ transplantation of patients.
Reason $R$: It reduces the cholesterol level in the blood.
Which option is correct for Assertion $A$ and Reason $R$?

Yeast has been used for the commercial production of:
$I.$ Ethanol
$II.$ Bread
$III.$ Toddy drink
$IV.$ Biogas
Choose the correct option.