One of the guards sighted a plane through binoculars that she could not identify. Is the correct answer.
The general point is "Carla is a pleasure to be around." This is non specific.
All other points outline specific attributes that support this statement, referring to her smile and willingness to listen and ask questions.
A nonrestrictive clause or a nonessential clause is basically an adjective that just adds extra or not needed information to a sentence. The meaning of that sentence would not change even if the clause was not there.
Word, pronunciation, definition and etymology are the standard and major parts of a dictionary.
