What is the difference between "can have + past participle " and "could have + past participle"?

How can a musical work be an argument

The adventures of tom sawyer, chapter 6 (excerpt) what does tom do to get sid’s attention? a) tom lies in bed as he tries to think of an excuse to miss school b) tom knocks a book on the floor to wake sid up c) tom tells sid that he is suffering from an infected toe and a loose tooth d) tom groans and says, “ when i’m gone…”, so sid will call for aunt polly’s how does sid react to tom as he pretends to die? a) so it becomes anxious and asks if tom is dying b) sid knows tom is faking but joins in with tom’s game c) sid takes tom seriously and makes a list of tom’s valuables d) sid knows tom is a lying and immediately runs to tell aunt polly

Emily is reading her friend's story. it uses transition words like and emily can tell that this story's organization is a) sequence of events b) cause and effect c) compare and contrast d) question and answer