Answer
C. Had a large base of support
edge
The error in the possessive construction is that, instead of passenger's, it should be "passengers'". The apostrophe should be after the letter "s" because the noun is in the plural form. The correct sentence would be "Passengers' concerns about cell phone use on planes are justified."
The sentence that best represents the function of a supporting sentence is, option B. It adds more details to the topic sentence. The supporting sentences make up the paragraph that talks about the main sentence. The supporting sentences not only add more information about the topic, but also add examples to further explain the main sentence.
there were weeds IN the flower garden
Authors might have something else in mind for what they are writing about.