THE MODAL VERBS HAVE TO, DON´T HAVE TO-SHOULD,OUGHT
H AVE TO REFERS ABOUT OBLIGATION OR SOMETHING THAT IT ´ S NECESSARY TO DO. She has to clean the floor I have to feed my dog
H E SAYS I HAVE TO DO MORE EXERCISE ( H E SAYS IT IS NECESSARY FOR ME TO EXERCISE MORE )
S HOULD IS USED TO GIVE ADVICE OR EXPRESS SOMETHING THAT IS A GOOD IDEA. CAN BE USED FOR GENERAL SITUATIONS AS WELL AS SPECIFIC You have a headache. You should take an aspirin. You should always consult a doctor before taking antibiotics
OUGHT TO This verb is used in the same way as Should. It expresses a weak obligation. Karen ought to be more careful We ought to go together