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问题 单项选择题 A1/A2型题

关于内毒素的叙述，不正确的是（）

A.内毒素由革兰阴性菌产生

B.内毒素不耐热

C.内毒素毒性较外毒素弱

D.内毒素的免疫原性较外毒素弱

E.内毒素经甲醛处理不形成类毒素

答案

参考答案：B

解析：内毒素较稳定，耐热，60℃耐受数小时，121℃，20min不被破坏。

单项选择题

Which of the following statements about the taxation of separate trading of registered interest and principal of securities (STRIPS) is FALSE（）

A. Implicit interest taxation is a paramount issue for pension plans.

B. A 10 -year Treasury note has 20 coupons and 1 principal payment.

C. The STRIPS program began in 1985.
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选择题

His father told me that he _____ for the United States three days _____.[ ]

A. has left; ago

B. had left; ago

C. left; ago

D. had left; before

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