词汇	fruitless labors
释义	fruitless labors 无收益的劳动
随便看	single track theory single-track theory single track tunnel single-track tunnel single track type pulley weight exerciser single track type pulley-weight exerciser single track vehicle single-track vehicle single traction single traction rod single trailing arm type single-trailing-arm-type suspension single train checking work single training sample single trait single traits single trait selection single-trait selection single tramway-type equipment single transaction access single-transaction access Single transaction itemsets combination single transducer operation single transferable vote single transfer device