【单选题】A company manufactures a product which requires four hours per unit of machine time. Machine time is a bottleneck resource as there are only ten machines which are available for 12 hours per day, five...
【简答题】把选项A、B、C或D填在空里。 new words: aquatic mammal 水栖哺乳动物 flipper /ˈflɪpə/ n. 鳍 cone shaped 圆锥状的 calves /kɑːvz/ n. (calf 复数 ) 幼仔,幼兽 boat propeller 船螺旋桨 aquatic species水生生物 1. How many species of dolphins are t...