A population of snails is separated when an eight-lane highway is built. After 50 years, the two separate populations can no longer interbreed. This describes the process of

speciation

Explanation:

When a population contains two separate groups that can no longer interbreed and produce fertile offspring, then speciation has occurred.

the illustration   that would give a reader a clear understanding of the text is a picture of men constructing the frame of a building.the frame is made of iron bars. the text describes the job of blacksmiths'. these were very organised and they had different names: "the driver" and "the heater". the text describes the way in which these men worked ; they worked iron pieces as if they were playing a sport. in fact, the text wants to show the men's skills. the text also puts some emphasis on the use of '' rivets'' in construction. this kind of nails were not always used in the construction of manhattan.

some examples:

"and with an underhand toss he hurled the smoking rivet straight at the catcher, who caught it in mid-air in his catching can." men's skills

"when the driver was ready for a new " the emphasis on the rivet ( special nail used in construction).

" it against a beam to remove any cinders, and jammed it into the waiting hole. " the emphasis on the rivet.

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.