什么是优化处理？优化处理又可进一步分成哪两个类型？各举2个常见方法。
Which two statements about the diffserv model are true？（） ["a class can be inentified as a single application .multiple applications with similar service nees.or be based on the source or destination ip addresses.","a drawback of the diffserv model is that it does not provide backward compatibility with devices that can only use the tos field.","diffserv uses the diffserv field in the MAC header to mark frames into behavior aggregates（BAs）","the diffserv field occupies the same eight bits of the mac header that were previously used for the tos field.","the first six high-order bits of the diffserv field are used to identify the resource reservation protocol（RSVP） value .","the primary goal of diffserv is scalabilty."]
铜元素的存在有助于提高带钢的（）。
食物中抗生素残留对人体主要危害有损害组织器官、（），（），（）和（）作用等五个方面。
如何预防肉鸡胸囊肿和腹水症？
压力容器的重大改造
