_______ confidence and patience, they failed to settle the difficult problem.

A．Lack in

B．Lacking of

C．Lacking

D．Having lacked

润扬大桥下江水深为20m，桥上一彩灯距水面30 m，则该彩灯的“倒影”距水面_____m；若江水上涨0.5 m，则该彩灯与其对应“倒影”相距_____m。