二、单项选择(15分)
﹙ ﹚21. — Would you like to go to the movies with me?
— I am sorry. I am busy with drawing umbrella on Internet.
A.an; aB. a; an C. an; the
﹙ ﹚22. He had to retire(退休)early _____poor health.
A, because of B. because C. so