1 must
2 have to
3 can,to be able to
4 may, might
1. must; had to
2. have to; had to
3. can; could; may; might; to be able to;
4. can; may
1 must
2 have to
3 can,to be able to
4 may, might
1. must; had to
2. have to; had to
3. can; could; may; might; to be able to;
4. can; may