－It’s Sunday today, so you        get up so early.－Yes, I can have a good rest.

–Carla _______ go to that historical museum after school when she was a teenager. --No wonder she is so familiar with it. 

Mr.Smith is on time for everything. How        he be late for the ceremony?

(2013·安徽高考)It ________ be the vocabulary that caused you the problem in the exercise because you know a lot of words.

(2013·湖南长沙四校二模)—Is the letter from your mother?—Yes.But she ________the letter herself，because she doesn’t even know one word.