The three main expeditions were plowing through seas infested with U - boats.三個(gè)主要遠(yuǎn)征部隊(duì)駛經(jīng)充滿潛艇的海岸.It's all to no purpose; I tell you that you are plowing the sand.這是徒勞無(wú)益的; 告訴你,你在枉費(fèi)心機(jī).When plowing, I plowed deeply ; whe...