How does a the opposition keep a check on the ruling party?

The Opposition’s main role is to question
the government of the day and hold them accountable. Opportunities for scrutinising the policies and administration of the Government are provided in Question Time, the Address- in-Reply debate, Budget debates, debates on legislation, notices of motion and No Confidence Motions. Members of the Opposition who are members of parliamentary committees have a further opportunity to scrutinise new legislation as part of the committee process.
The Opposition also utilises the media to reach the electorate with its views and to establish an identity as an alternative government.

Ithink the answer is b : )