题目

    In recent years，American students have fallen behind in many subjects like math，science and reading. In 2005，the U.S. was number nine among the developed countries in the number of students graduating from high school. American education officials are searching for new ways to help students learn again. One tool that is getting some attention is the use of video games. Sixteen­year­old John Diaz says he loves playing video games but doesn't like traditional schoolwork. During his summer vacation，Diaz is continuing his studies at home. That is because his courses are av14．下列数据中，最接近实际的是（　　）A．中学生正常步行的速度约为1.0m/sB．一名中学生的质量约为5000gC．中学生脉搏跳动一次的时间约3sD．教室空间的高度约为500dm