题干
17．—Is there any better way to help my son get rid of the habit of playing computer games?
—To tell you the truth, it’s very hard. But we_______on this problem to improve the situation.
A：were working
B：had worked
C：are working
D：had been working
答案(点此获取答案解析）
C
的左、右焦点分别F1、F2，O为双曲线的中心，P是双曲线右支上的点，
的内切圆的圆心为I，且⊙I与x轴相切于点A，过F2作直线PI的垂线，垂足为B，若e为双曲线的率心率，则 （ ）