Which sentence contains an essential adjective clause?

the coach explained the rules that the officials revised in 2010.
the coach, an expert in the sport, explained the revised rules to us.
after explaining the rules to us, the coach released us to the field.
the officials revised the rules, which the coach explained to us before practice.

given the fact that the question is about the detail that best support the idea that oppressive leaders use   propaganda to achieve thir goals,   the first option does not refer to any kind of propaganda, since it only tells about that the milk and the windfall apple should be reserved for the pigs. in the second option, that is, "snowball and napoleon sent out flights of pigeons whose instructions were to mingle with the animals on the neighbouring farms, tell them the story of the rebellion, and teach them the tune of "beasts of england". it can be identified that the oppressors make use of the propaganda, which is represented by the pigeons, and the information they have to tell other animals about what was happening in the farm in order to get their objectives. for that reason, the right answer is the second option, taking into account that the third option do not refer to propaganda since it only talks about that they did not want jones back. and, finally, the last option refers to the result of the given news, but it does not mean about the propaganda they used to achieve their goals.