my textbook states that the executive power is exercised by the governor-general on the advice of the government, and therefore is largely exercised by the government. for simplicity's sake, I would say that the government is included in the executive division of power. as with duck's question, I don't think they would look too deeply into it, because as long as you state that it's exercised by the governor-general on the advice of the government, you've covered who the power is wielded by.
hmm, just now thought about it, and i suppose that the government can't officially be in the executive body of power, since the entire purpose of the separation of powers is to keep the three divisions seperate. Government's part of the legislative, and if they were officially included then the separation of power isn't doing its job
but don't go too deeply into it. I don't think it would be a major concern on the exam, and if so, just show them that you do understand the material.