菌体的倍增时间是（）增加一倍所需要的时间。
A.细胞质量
B.菌体浓度
C.菌体种类
D.呼吸强度
参考答案：A
用所给词的适当形式填空
1. What are your parents (read) now?
2. Evervone (be) at home last Saturday.
3. What about____(sit) under the big tree?
4. Our English teacher____(leave) school an hour ago.
5. Look out! It's (rain). We can't go out.
在如图所示的四幅图中，正确标明了带电粒子所受洛伦兹力f方向的是（ ）
A．
B．
C．
D．
