- She was studying the textbooks all night long
 - The pie was cut into six equal pieces
 - Today the teacher is allowing the students to leave class a few minutes early
 - The class is taught every other semester
 - Tom is bringing some drinks to the party
 - The sick child was taken to see a doctor
 - The children are swimming in the backyard pool
 - The teacher is preparing a difficult exam for the students
 - Dinner is served from 6:00 to 8:00
 - She is smelling blooming flowers
 - Elizabeth was watching TV when the earthquake happened
 - Irene may be helping her mother in the kitchen now
 - They must have visited their sick friend
 - Samuel has finished his study at a university
 - She might have got an accident when tiding her motorbike so fast
 
Base Form Verbs after Modals
- you should try to respond politely
 - everyone must leave the room immediately
 - i could sit on the beach for hours
 - she will ask you may difficult questions
 - you can look at the book, but you cannot borror it
 - he may lie to you because he is not very truthful
 - he knew that he would forget the phone number
 - the weatherman said thet it might snow tonight
 - perhaps we could buy a new car this year
 - this course will satisfy the graduation requirement
 - you must not walk on the grass
 - they had to sell their house
 - we thought he might sell the house
 - i think the bill could be expensive
 - he may be wrong, you know
 
sumber:
http://www.grammar.cl/english/modal-verbs.htm
http://www.toeflskill.com/2011/06/problems-with-modals-skill-18.html