The nurse is caring for four clients on a step-down intensive care unit. The client at the highest risk for developing nosocomial pneumonia is the one who （）.

A．has a respiratory infection.

B．is intubated and on a ventilator.

C．has pleural chest tubes.

D．is receiving feedings through a jejunostomy tube.

在烧结过程中，生产以铁酸钙为主要粘结相的烧结矿必须具备三个必要条件，它们分别是（）、低温、氧化气氛。