Let's take________(photo), OK?
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Two ____ (family) live in this building.
写出下列单词复数形式1.house__________2.village________3.map_______4.orange_________(橙汁)5.bag_________6.zoo_________7.brush__________8.bus__________9.city_______10.box______11.baby__________12.police________13.factory________14.glass___________(杯子)15.knife_________16.Chinese_________17.fish___________(鱼肉)18.sheep_______19.toy20.radio_____
滚子链由______、______、______、______、______组成。(第88页)
链条上相邻两销轴的中心距称为节距。它是链条最主要的参数,节距越大,承载能力越____,但链条的各部分尺寸和重量也____。(第89页)