—— Hurry up. The bus is coming!

—— Oh, no, we mustn’t cross the street ______ the traffic lights are green.

A. after B. since C. when D. until

---Hurry up. The bus is coming.

---Oh, no. We mustn't cross the street ________ the traffic lights are green.

1. A.
   after
2. B.
   since
3. C.
   while
4. D.
   until