Speculation about possible situations

1.

Speculation about possible situations
He might be a professional football
player because he is so good
He might have been professional football player
but I’m not sure

2.

Speculation about situations that we confident in
He can’t go in school. Нe's sick
He can’t gone in school because I saw
that he was sick

3.

Speculation in the present
She could be a student because I saw that
she learnt something
She must be a student. She wore school unifor,