A client with acute respiratory failure is intubated and placed on mechanical ventilation. Which intervention is most appropriate when suctioning the client ？（）
A．Insert the suction catheter while applying suction.
B．Apply suction until all the secretions have been removed.
C．Use the same catheter to first suction the mouth, then the endotraeheal tube.
D．Preoxygenate with 100% oxygen before suctioning.
