"Did you walk? No. We ran."
Translation:SuyIt'a'? ghobe'. maqet.
bI- is used for "you (singular)". Su- is used for "you (plural)". If the sentence had only been "Did you walk?", then there would have been no way for you to distinguish whether the "you" was singular or plural and both answers would have been accepted. However, in this sentence, the answer ("We ran"), tells you that multiple people are answering, so the "you" must have been plural and Su- would be the correct prefix in the question.
No. Many languages only conjugate the verbs based on the subject (the one doing the action of the verb). Klingon prefixes include information on the subject, but also include information on the object (that the action is done to). The prefixes Da-, bo- and wI- all indicate that there is a specific object. However in these sentences, no object is indicated in the English. There isn't anything being walked (to) or being run (to) and so there are no objects for these verbs and you wouldn't use a prefix with an object.
There are prefixes that don't include objects. These should be interpreted as saying that the verb is being done generally or at least not to a specific object. The prefixes Su- and ma- do not include objects and so are appropriate for these sentences with yIt and *qet".