Which organism is useful for producing a chemical that inhibits immunity during organ transplantation?

Read the following statement having two blanks $(A$ and $B)$:
$A$ drug used for $A$ patients is obtained from a species of the organism $B$. It helps in clearing blood clots inside the blood vessels.
The one correct option for the two blanks is:

Yeast are economically important because they

The process which the yeast cells perform is called:

Which of the following pairs is mismatched?

Choose the correct pair.