题干
We work during the week, but weekends and evenings are usually____.
A：vacant
B：casual
C：empty
D：clear
答案(点此获取答案解析）
D
We work during the week, but weekends and evenings are usually____.
A：vacant
B：casual
C：empty
D：clear
表示的平面区域是一个三角形，则实数s的取值范围是（ ）