A liner in riveted construction of a vessel is a(n)（）. ["small plate which fills the aperture between riveted strakes and the vessel framing","backing plate which is used to level the strakes while riveting，and then removed","internal frame to which the side shell is riveted","seam that is welded after riveting is completed"]
个人业务产品助销员每年至少电话联系或上门拜访（）个新客户。 ["100","300","500","1000"]
《防止电力生产重大事故的二十五项重点要求》中对防误闭锁装置有哪些规定？
注册商标中含有的（），注册商标专用权人无权禁止他人正当使用。 ["本商品的通用名称、图形、型号","直接表示商品的质量、主要原料、功能、用途、重量、数量","地名","官方标志、检验印记"]
个人业务产品助销员每年开展市场调研活动，提交调研报告不少于（）份。 ["20","10","2","1"]
怎样使用化学除草剂？
