<span style="color:#800080;">1-A bus with twelve passengers had an accident. We are trying to contact the bus. <b>We don't know if one of the passengers is alive.</b></span><br/><br/>Can't this have two different meanings:<br/><span style="color:#ff0000;">a-We don't know if any of the passengers are alive.</span><br/><br/><span style="color:#0000ff;">b-We do not know if a specific passenger is alive. We are sure that the eleven others are alive, We have doubts about one of them.</span><br/><br/>Gratefully,<br/>Navi.