Answer:
B) a row of letters in a visual array
Explanation:
The experiment conducted by Sperling was intended to proof the existence of Visual sensory memory and to find out whether this memory have a certain set of duration or capacity between individuals.
In the experiment, He made the subjects to look at a computer and the screen will briefly show a row of letters to the subjects. The result show that The subjects could see the letters and recall them, proving the existence of visual memory. But the duration of this memory is so short since most subjects only capably to remember those letters for a couple of minutes.