题干
When ______ comes to golf, I know nothing and I have no interest in it.
A：thi
B：that
C：it
D：one
答案(点此获取答案解析）
C
数为k，小球重力为G，平衡时球在A位置，今用力F将小球向下拉长x至B位置，则此时弹簧的弹力为( )