My grandfather, who in the beaching field all his life is retiring next month． [

My grandfather, who ________ in the beaching field all his life is retiring next month．

serving

is serving

had severed

has served

试题答案

答案：D

who引导定语从句，后面缺宾语，因此排除A项。serve“服务”，可以是及物动词也可以是不及物动词。根据后面“下个月退休”可知，现在他的祖父还在beaching field工作，这样排除了C项。is serving现在正在服务(强调现阶段正在进行的动作)；has served一直服务(强调过去的动作一直延续到现在)，故D项为最佳答案。语意为：我的祖父在海滨工作了大半生，下个月要退休了。