Which organism is used for the production of penicillin?

Assertion $A$: $Ernest \text{ Chain}$ and $Howard \text{ Florey}$ improved the production of penicillin.
Reason $R$: Penicillin was obtained from the fungus $Penicillium \text{ notatum}$.
Which option is correct for Assertion $A$ and Reason $R$?

Assertion: Vitamin $B_2$ is found in cereals,green vegetables,brewer's yeast,egg white,milk,and liver.
Reason: It can be commercially produced by some yeasts.

The large holes in Swiss cheese are due to the production of a large amount of $A$ by a bacterium $B$. Here $A$ and $B$ refer to:

Which steroid is useful for transformation?

Which cheese is characterized by the presence of large holes?