电池是把化学能转化为电能的装置，发电机是把机械能转化为电能的装置。
参考答案：对
—______ are the twin sisters?
—They are fourteen.[ ]
A. How old
B. How much
C. How many
D. How
能在麦康凯琼脂上生长并形成无色菌落的病原体是（）.
