1.Speak loudly (loud)so that everyone can hear you clearly.修饰动词用副词
2.Ling Tao reads the text -louder(loud)than Zhang jian.有than,所以用比较级loud is adv.,too.1.Speak loudly/loud (loud)so that everyone can hear you clearly. 修饰动词用副词2.Ling Tao reads the text -louder (loud)than Zhang jian. 有than，所以用比较级loud adj/adv但做副词时只能修饰简单的speak/say/sing等直接能发音的动作loudly adv 可接上能发出声音的所有各种动作，如关门，踢球等等，也就是说它修饰的动词范围更加广泛。所以两种都可以