One of the elements of clause structure
Carlos had such a captivating smile.
The difference between the words swarmed and assembled should give you a clue as to what the answer is. Swarmed means to move somewhere in large numbers, usually crowding around something of interest to get a closer look. Assembled means to gather together in one place for a particular reason. This is usually done in an orderly fashion.
D. A line of safety goggles that damage the eyes
The plot is always the overriding idea in fiction.
