伤寒沙门菌产生()
A.内毒素
B.外毒素
C.神经毒素
D.细胞毒素
E.红疹毒素
参考答案:A
Everyone here will thank the firefighters for the things they have done to prevent fires _______ the environment safer.
A.make
B.to making
C.to make
D.from making
原始社会,人类依附于生物圈,人与生物圈保持______________。