Efficiency and redundancy are contradictory characteristics of linguistic systems; however, they can be used together...

I find myself diagramming almost every sentence in the stimulus. However, the answers diagram less than I do. Should I only look out for the keywords when diagramming or how do I know when I am diagramming parts of the stimulus that I would not need to determine the answers? For example, in this question, I diagrammed the first 2 sentences about while efficiency and redundancy are contradictory, they can work together for useful and reliable communication. But, this was not diagrammed in the response even though there are words like "and"