以重组DNA技术为核心的基因工程正在改变着人类的生活。请回答下列问题。
大肠杆菌是理想的受体细胞,这是因为它()。
参考答案:繁殖快、为单细胞生物、遗传物质相对较少
什么叫磁通?
— There were already five people in the car but they managed to take me as well .
— It ____ a comfortable journey .
A.can''t be
B.shouldn''t be
C.mustn''t have been
D.couldn''t have been