[名词解释]
R_4s

关于外毒素的叙述，下列哪项是错误的() ["A．是活菌释放至菌体外的一种蛋白质","B．由革兰阳性菌及少数革兰阴性菌产生","C．抗原性强","D．毒性强","E．性质稳定、耐热"] 质量保证质量控制混凝土的骨料是指()。 ["水泥","砂子","石子","石膏","水"] 病原菌侵入血流并在其中大量繁殖，产生毒性代谢产物，引起严重的全身中毒症状称为() ["A．毒血症","B．败血症","C．菌血症","D．脓毒血症","E．内毒素血症"]