The correct answer would be the first option: Good leaders treat everyone the same.
This passage tells the story of goatherd that <em>decided to treat better wild goats than his own</em>, just to see if they would decide to stay with him. He had taken all of the goats inside a fold to spend the night and, after the snow, when he took them outside, the wild goats left and told him that they were leaving because he treated them better than the ones that had been with him for such a long time, and <em>that proved he lacked character and wasn't trustworthy.</em> <em>"(...) it is plain also that if others came after us, you would in the same manner prefer them to ourselves"</em>, the wild goats said, explaining why they chose not to stay with the goatherd. The goatherd's attitudes <em>weren't those of a good leader, who treats everyone the same way and therefore inspires trust.</em> This is why "Good leaders should treat everyone the same" is the theme most exemplified in this passage.
The correct answer couldn't be the second one,<em> "Kindness inspires others to be kind</em>", because, although the goatherd could be considered kind when he decided to take the wild goats inside a shelter along with his own, the story shows<em> his selfish reasons</em> to do so. Thus, the story isn't about inspiring kindness, but about not trusting people who take action based on their own reasons and do not value those around them.
The correct option couldn't be the third one, <em>"Strangers cannot always be trusted"</em>, because, although the goatherd was a stranger to the wild goats, the <em>reason why he couldn't be trusted was his showing different treatment towards the goats,</em> by treating better those he didn't know so well, and neglecting those who had been with him for a long time. So, that couldn't be the most exemplified theme in the passage.
The correct option couldn't be the fourth one, <em>"Ingratitude leads to unhappiness"</em>, because the wild goats didn't show <em>any signs of ingratitude towards the goatherd, nor became unhappy</em> when they left him. Also, he wasn't necessarily ingrateful with his own goats, he just didn't treat them as well as they deserved. Therefore, this couldn't be the most exemplified theme in the passage.
