What makes this study different from previous research which also saw cortisol synchronization in dogs? ( )

参考解析：

细节题。第三段Hair records the level of the stress hormone cortisol in the body over time so by analyzing these hairs, the team could figure out just now much stress both the owners and their pets were under long-term. 毛发记录了随着时间的推移人体内的皮质醇水平，因此通过分析这些毛发，研究小组可以得出主人和他们的宠物目前所承受的长期压力。第五段But this finding was something new. "This is the first time we've seen a long-term synchronization in stress levels between members of two different species. We haven't seen this between humans and dogs before."表明狗和主人的压力水平是一致的: 主人压力越大，狗的压力也越大。故本题正确答案选A。