题目

阅读理解When I was 14, I'd pick my youngerbrother up from school, Jen says. I'd be in charge of checking hishomework and making sure that he was fed until our parents got home. That is one of the things that led Jen, a StanfordGraduate School of Business student, to become interested in how people'sperception of their own age can influence their actions.That curiosity led her to team up with Szu-chiHuang, an associate professor at Stanford, on a series of experiments in whichthey shifted participants' perception of their own age in order to study theeffects on their willingness to help str人的心脏位于胸腔的中央偏______下方，两肺之间，大小与拳头相近．经常进行体育锻炼的人心肌发达，心输出量大，心率比正常人要低．儿童时期心率要高．