流行病学中的偏倚是指
A．随机误差
B．抽样误差
C．系统误差
D．信息误差
E．分类误差
参考答案：C
解析：流行病学中的系统误差又称为偏倚。
用所给动词的适当形式填空。
1. You should always (speak) English in class.
2. Why don't you (write) down the correct words?
3. It's a good idea (check) your vocabulary notebook.
4. How about (listen) to the radio in English?
5. Try not (translate) every word when you learn English.
6. Everyone should (have) a pen friend.
平面上动点M到定点F（3，0）的距离比M到直线l：x+1=0的距离大2，求动点M满足的方程．
