Thearmyorganizedteamstodigoutthosewhoweretrappedandtoburythedead.
这句话转换成:Thearmycametohelp-diggingouttrappedpeople,buryingthedeadandrescuingminers.
请从语法角度解释为什么这里dig,bury,reacue三个词转换后要变成ing形式,