CAN YOU PLEASE REVIEW ANSWER,YOU GAVE ME D AND IT IS WRONG

If an oligopolist is part of a cartel that is collectively producing at the monopoly level of output, then the oligopolist, being self-interested, will:

Select one:

a.increase production and push prices down

b.lower production and drive up prices

c.do nothing, thus allowing the cartel to realise monopoly profits

d.do none of the above