If you saw another kid ride her bike too fast around a corner and fall down, you might ride your bike more slowly on that turn. Yes, we humans are very sensitive to others' mistakes. And the same is true for other animals. Animals mess up all the time. They might eat poisonous leaves, fall off a tree or let their prey   slip away. By watching others fail, an animal can avoid making the same mistakes, thus improving its chance of survival. Scientists suspected that one part of the brain helps animals process information about others' errors. Cells in that part appear to become more active when a person sees someone else making a mistake. But researchers didn't know whether individual cells in this part of the brain play different roles in _ errors. To investigate the brain's response to errors in more detail, the researchers taught a game to two macaques, a type of monkey. One monkey could press a yellow or green button while the other watched. If the first monkey pressed the right button, the team gave both animals a treat. Every couple of rounds, the two monkeys switched roles. Meanwhile, the scientists monitored individual cells in the animal's brains. When the first monkey messed up the game by pressing the wrong button, a group of cells in the second monkey's brain fired. But if the second monkey also made the wrong choice during its turn, some of the cells in that group didn't respond. Those unresponsive cells reacted specifically to mistakes made by others, not to the monkey's own mistakes. Scientists believe other parts of the brain also might help people process information about another's errors. "You start to think about this other person and see things from his angle. " Ellen de Bruijn, told Science News. She studies the brain at the University of Leiden in the Netherlands. In the experiment mentioned, those unresponsive cells are only sensitive to   _  .
the same buttons others' mistakes one's own mistakes the monkey's brain
Question: If you saw another kid ride her bike too fast around a corner and fall down, you might ride your bike more slowly on that turn. Yes, we humans are very sensitive to others' mistakes. And the same is true for other animals. Animals mess up all the time. They might eat poisonous leaves, fall off a tree or let their prey   slip away. By watching others fail, an animal can avoid making the same mistakes, thus improving its chance of survival. Scientists suspected that one part of the brain helps animals process information about others' errors. Cells in that part appear to become more active when a person sees someone else making a mistake. But researchers didn't know whether individual cells in this part of the brain play different roles in _ errors. To investigate the brain's response to errors in more detail, the researchers taught a game to two macaques, a type of monkey. One monkey could press a yellow or green button while the other watched. If the first monkey pressed the right button, the team gave both animals a treat. Every couple of rounds, the two monkeys switched roles. Meanwhile, the scientists monitored individual cells in the animal's brains. When the first monkey messed up the game by pressing the wrong button, a group of cells in the second monkey's brain fired. But if the second monkey also made the wrong choice during its turn, some of the cells in that group didn't respond. Those unresponsive cells reacted specifically to mistakes made by others, not to the monkey's own mistakes. Scientists believe other parts of the brain also might help people process information about another's errors. "You start to think about this other person and see things from his angle. " Ellen de Bruijn, told Science News. She studies the brain at the University of Leiden in the Netherlands. In the experiment mentioned, those unresponsive cells are only sensitive to   _  .
A. the same buttons
B. others' mistakes
C. one's own mistakes
D. the monkey's brain
Answer: