N20的特点是
A．在体内代谢性高B．对气道刺激性强C．化学性质不稳定D．血气分配系数低E．易燃烧、爆炸
参考答案：D
Hiking by oneself can be fun and good for health.It may also be good for________building.[ ]
A. respect
B. friendship
C. reputation
D. character
放射性核素显像检查诊断阳性率较低的是（）
A.肝脓肿
B.甲状腺肿瘤
C.大肠癌
D.骨肿瘤
E.脑肿瘤
