题干
It's difficult for me after the 20-kilometer hiking.
A：breath
B：breathe
C：to breath
D：to breathe
答案(点此获取答案解析）
D
It's difficult for me after the 20-kilometer hiking.
A：breath
B：breathe
C：to breath
D：to breathe
，则f（0）等于（ ） 
