1,-----you open the window,please a,could b,can c,would d,should 2,i----see a doctor ,because i felt very sick a,have to b, had to c,must 3,we use -----to say something is possible or allowed somebody has the ability to do it 4,we use------ to say that we believe something is certain 5,we use ------ to mean it is a good thing or the right things to do
