题干
Mary is a ________ girl, and she can sing ________.
A：good; good
B：well; well
C：well; good
D：good; well
答案(点此获取答案解析）
D
Mary is a ________ girl, and she can sing ________.
A：good; good
B：well; well
C：well; good
D：good; well
，则a的取值范围是（ ）