Answer: What is missing from the sentence provided is D. a predicate.
Explanation: "The sparkling blue bicycle with the brand new tires and comfortable seat" is a sentence fragment because an essential part of the sentence is missing: the predicate. In other words, the sentence provided does not express a full thought because it needs a predicate, that is to say a verb that indicates what the subject ("The sparkling blue bicycle with the brand new tires and comfortable seat") is or that indicates what is the change that the subject has gone through. For example, the sentence could be completed by adding the predicate "was stolen".