科学家合成出了一种新型氧分子，其表达式为O4，对其说法正确的是 A．是一种单质

Most computer systems are (165) to two different groups of attacks: Insider attacks and outsider attacks. A system that is known to be (166) to an outsider attack by preventing (167) from outside can still be vulnerable to the insider attacks accomplished by abusive usage of (168) users. Detecting such abusive usage as well as attacks by outsides not only provides information on damage assessment, but also helps to prevent future attacks. These attacks are usually (169) by tools referred to as Intrusion Detection Systems.

（166）处是（）

A.reliable

B.secure

C.indestructible

D.steady

女性，58岁，因慢性阻塞性肺疾病呼吸衰竭住院，行气管插管机械通气支持。1天后神志已转清，PaCO₂由10．6kPa（80nmfftg）降至5．1kPa（38mmHg）

为预防或避免呼吸机相关肺炎，应特别注意（）

A.避免使用H₂受体阻滞剂，防止胃液pH升高

B.防止呕吐物吸入

C.预防性应用高效、广谱抗生素

D.静脉应用高剂量丙种球蛋白

E.把患者安置于隔离病室

颈部肿块最多见于（）

A.甲状腺肿

B.甲状腺肿，肿大的淋巴结

C.神经纤维瘤，神经鞘瘤

D.甲状腺肿，颈动脉瘤

E.肿大的淋巴结

已知某砝码质量的测量结果为m=(99.981±0.003)g，若置信概率为99.73%，则该砝码质量测量的标准不确定度为( )。

A．0.001g

B．0.0015g

C．0.0017g

D．0.003g

钢材在高温下承受应力作用时，在保持总变形量不变的条件下，应力随着时间的增长逐渐降低的现象称为（）。