表推測：
must, may, might, could, can, can’t
must“一定”，可能性，常用于肯定句。
There is the door bell, it must be Tom. 門鈴響了，一定是湯姆(來了)。
may / might“也許”一般用于肯定句， may比might可能性大。
She is coming to us. She might be our new teacher.
can / could“可能”could比can語氣更委婉。但can多用于否定。
You could be right, but I don’t think you are.
The light in the office is off. The teacher can’t be there now.
must, may, might, could, can, can’t
must“一定”，可能性，常用于肯定句。
There is the door bell, it must be Tom. 門鈴響了，一定是湯姆(來了)。
may / might“也許”一般用于肯定句， may比might可能性大。
She is coming to us. She might be our new teacher.
can / could“可能”could比can語氣更委婉。但can多用于否定。
You could be right, but I don’t think you are.
The light in the office is off. The teacher can’t be there now.