Correct answer:
No cruce la calle
We use the imperative mood to tell someone to do something in a direct manner. Put another way, sentence in the imperative mood are commands. So the sentence no cruce la calle is a formal command because the word cruce is the conjugation of the verb cruzar that matches the formal subject pronoun usted (formal you). Therefore, we have:
No cruce la calle (don't cross the street)