公路上行驶的两汽车之间应保持一定的安全距离，当前车突然停止时，后车司机可以采取刹车措施，使汽车在安全距离内停下而不会与前车相撞，通常情况下，人的反应时间和汽车系统的反应时间之和为1s，当汽车在晴天干燥沥青路面上以108km/h的速度匀速行驶时，安全距离为120m，设雨天时汽车轮胎与沥青路面间的动摩擦因数为晴天时的 $\frac{2}{5}$ ，若要求安全距离仍为120m，求汽车在雨天安全行驶的最大速度．

考古学上通过碳-14原子测定文物年代。碳-14和碳-12原子在原子结构上的不同之处是____，它们的原子质量比是____。

阅读理解
    Interested in getting ahead over the summer? Then stay on course by taking advantage of Alvernia's Summer Session. It lets you get ahead with a large selection of undergraduate and graduate courses. You can attend the class in classrooms or online, or you can take blended (混合的) courses if you like. We offer several flexible sessions at all three locations in the summer to help move you closer toward graduation. All courses are officially recognized and credits you earn are transferable (可转移的).
    You don't have to be admitted to Alvernia to take classes this summer. Our Summer Session is open to all Alvernia students and to students from other colleges and high schools, as well as adult professionals and lifelong learners.
    And if you're taking a course with us. You'll have full access to the library, gym, cafes, and computer labs. Alvernia's Summer Session is an ideal option for students who:
    Want to lighten their course load for coming semesters (学期).
    Stay on track to complete their degree on time.
    Plan to earn additional credits now to graduate a semester early.
    Had trouble with a course during a past semester and need to retake it.
    Just want to take a course for fun.
    To find out what financial aid options might be available to you, contact the Office of Student Financial Planning by emailing financialaid @ alvernia.Edu or calling 610-796-8356.
    We offer several flexible sessions to help fit your busy lifestyle. You can take classes and also enjoy your summer! (See courses for specific dates by visiting alvernia.edu/financialaid)

如图，⊙O的直径为10，弦AB的长为8，M是弦AB上的动点，则OM的长的取值范围(         )

　　    

多种激素共同调节人体生理活动。下列叙述正确的是(　    　)