标准预防认为以下病人哪个具有传染性：（）

单项选择题传染病分几类：（）

单项选择题What is the purpose of phase I clinical trial:() A、This is the first time the drug is tested in humans. B、Usually, health volunteers take part in these trials. C、Escalating doses of the drug are administered and side effectsmonitored, to establish the maximum tolerated dose (MTD) and recordthe dose limiting toxicities. D、This is often inappropriate and patients with advanced diseaserefractory to conventional treatment are offered participation.