Answer:
The answer is: A group of people acting together
Step-by-step explanation:
As you can see, the first option along with the last options, are the only options that are actually nouns. The other options are adjectives, so the preposition "of" doesn't allow the following word to make sense with an adjective, see it this way: The efficient of government... sounds odd right? It´d rather be, the efficient government... without "of" same happens with the second option.
On the other hand, the last option is the least possible for it is the literal meaning of "machine" and well, in this context that isn't the point. We're talking about a machine as of an organization, a system, a group of people; and well, that's what the government is.