Sube esa calle dos cuadras. La oficina está a la izquierda.
Why?
Suben means "they climed/ they went up the...". We're trying to give directions to someone here and not tell them where someone went.
Suba is referring to a female. In this sentence, it doesn't refer to a specific gender so we wouldn't use this in the sentence.
So that's how B. Sube is right.
Hope this helps!~
