While assessing a 2-month-old child’s airway, the nurse finds that the child isn’t breathing. After two unsuccessful attempts to establish an airway, the nurse should（）

A. attempt rescue breaths.

B. attempt to reposition the airway a third time.

C. administer five back blows.

D. attempt to ventilate with a handheld resuscitation bag.

目镜10╳，物镜40╳，那么看到的物像放大倍数是（）。