Choose the correct preposition to fill in the blank in the following sentence :
She should have been promoted _______monitor _________the class.

Correct option is A

The correct answer is (a) as ; of.
In this context:

• "Promoted as" correctly introduces the title or role being assigned — here, monitor.

• "Of the class" is used to show association or belonging, meaning the monitor assigned to a particular class.

So, the full sentence means that she should have been given the position of monitor assigned to the class.