In the phrase ,<em>The</em> wingspan, the definite article refers specifically to the condor's wingspan. If we say: "Big birds' wingspans have different lenghts", we are generalising our idea of wingspans . We are talking about the wingspans of birds in general, so we are not using <em>the . </em>But, if we want to talk about a bird in particular, we have to make the information definite and use the definite article.
Based upon the given answer choices, the two that best answer and fit the question are; The author is a well-know expert on the topic. The information comes from a respected university website.
