与志贺毒素致病作用类似的毒素是
A.肉毒外毒素
B.大肠杆菌内毒素
C.霍乱外毒素
D.金葡萄球菌外毒素
E.伤寒杆菌内毒素
参考答案:C
“θ=0”是“sinθ=0”的______条件.
句型转换。
1. This is my friend,Gina.(改为否定句)
____________________________________________________________
2. That is my sister.(改为一般疑问句)
3. These are my English books.(改为单数形式)
4. Is he your brother?(作肯定回答)