to listen
句意:听这样一个无用的报告是多么浪费时间啊!
根据观察句子的结构及联系句意,可知此句按正常的语序应是To listen to such a useless report is a waste of time.
to listen to such a useless report 整个这一长串是动词不定式作主语,太长了,头重脚轻不好看,所以用it来代替,变成:It is a waste of time to listen to such a useless report.
结合题干,然后又变成感叹句,所以把a waste of time放到前面,加上引导词what,就变成:What a waste of time it is to listen to such a useless report!
故填:to listen