Passage (1) Calling someone a rat may be complimentary. (2) In one experiment, University of Chicago neuroscientist Peggy Mason placed 30 pairs of rats in pens. (3) One rat was caged in the middle of the pen, while the other was free to run around. (4) Eventually, 23 of 30 rats liberated their peers by pushing the cage door open with their heads or leaning against the door until it tipped over. (5) In another experiment, Mason gave rats access to two cages: in one cage was another rat; in the other was a pile of chocolate chips. (6) The rats eating the chocolate themselves. (7) Instead, most of the rodents opened both cages and shared the sweets. (8) "In rat land, that is big," Mason says, claiming that this study is the first to show altruistic behavior in rodents. (9) Not all scientists agree with the conclusion Mason drew from the experiment, however. (10) The jailbreaking rats might have only been trying to silence their cohorts' distressing alarm calls. (11) Mason counters that the alarm calls from the caged rats were not frequent enough to motivate their peers, but both parties are speculating at this point. (12) Mason's new study is one of many that are changing how scientists think about empathy and altruism, namely: that such characteristics are not limited to people, as they once thought. (13) It now seems that many animals have evolved instincts to help others. Question Which is the best version of the underlined portion of sentence 12 (reproduced below)? Mason's new study is one of many that are changing how scientists think about empathy and altruism. namely. that such characteristics are not limited to people, as they once thought. (as it is now) altruism: namely altruism, namely; altruism-namely,