---Look! So many colorful bicycles in two lines over there.
---They’re for public. This ______ of green smart traffic is everywhere in Xiangyang city.
A. number B. pair C. kind D. piece
---Look! So many colorful bicycles in two lines over there.
---They’re for public. This ______ of green smart traffic is everywhere in Xiangyang city.
A. number B. pair C. kind D. piece
C