Answer:
a. Rao indorses his payroll check in blank.
Step-by-step explanation:
There are many types of indorsements, and out of them one is "Trust Indorsement"
Trust Indorsement is an indorsement to a person who can use the funds for the benefit of the indorser.
Example:
Brian indorses a check to his employee Denny "Payable to Denny, as agent for Brian", This is an example of trust indorsment.
Option b and c are clearly examples of trust indorsements in which you can notice that Rao has indorsed his lawyer and accountant "as agent for Rao".
Whereas, option a is NOT a trust indorsment but rather a "Blank Indorsement"
Blank Indorsment is an indorsement that doesn't have any particular indorsee and only has a signature on it.