Guessing and making hypothesis

Read this link as an intro: http://esl.about.com/library/grammar/blmodalprob.htm

When we aren't 100% of something we want to say about a situation we guess or make hypothesis.

To express it, we use this 'Guessing pyramid':

M U S T ( 99% probable) +
C A N (85%)
M A Y (50%)
M I G H T
COULD (10%) -

CAN'T (100% NO WAY!!!)

GUESSES or PROBABILITIES ABOUT PRESENT SITUATIONS

For example:

I am waiting for Julie with another friend, David. I ask: 'Where is Julie?' David guesses:

She must be on the bus. (I'm almost sure this is a good guess) She could be lost.
She may be in the wrong room.
She can’t be at home. (I'm almost sure this isn't possible)

http://www.oup.com/elt/global/products/headway/intermediate/a_grammar/unit09/hwy_int_unit09_1/

GUESSES or PROBABILITIES ABOUT SITUATIONS HAPPENING NOW

For example:
I am waiting for Julie with another friend, David. I ask: Why hasn't Julie arrived? What is she doing?' David guesses:

She must be coming by bus. (I'm almost sure this is a good guess)
She could be working at her office.
She may be eating with her family.
She can’t be partying with other friends! (I'm almost sure this isn't possible)

GUESSES or PROBABILITIES ABOUT PAST SITUATIONS

For example:

You: Where was Julie last night? David guesses:

She must have forgotten about our date.
She might have worked late.
She could have taken the wrong bus.
She may have felt ill.
She can’t have stayed at home.

http://www.oup.com/elt/global/products/headway/intermediate/a_grammar/unit09/hwy_int_unit09_2/

Exercises:
http://www.englishpage.com/modals/interactivemodal1.htm
http://www.englishpage.com/modals/interactivemodal4.htm
http://www.englishpage.com/modals/interactivemodal7.htm

TASK

Your English Teacher hasn't come to give classes this week. You went to ask in the coordination but they don't know any information.

What might have happened to her?
Where might she be?
What might she be doing?