—How long have you been studying at this school?
—I have been studying here ________.
A：since I was thirteen years old
B：when I was thirteen
C：at the age of thirteen
D：after I was thirteen
________ woman with sunglasses is _______ English teacher in New Star High School.
小林同学为了在体育中考获得好成绩，每天早晨坚持练习跳绳，临考前，体育老师记载了他5次练习成绩，分别为143，145，144，146，a，这五次成绩的平均数为144．小林自己又记载了两次练习成绩为141，147，则他七次练***均数为____．
先生讲得很详细，大家听得很认真。
后来，有个同学问孙中山：“你向先生提出问题，不怕挨打吗？”
孙中山笑了笑，说：“学问学问，不懂就要问。为了弄清楚道理，就是挨打也值得。”
