Bernard: For which language, and thus which frequency distribution of letters and letter sequences, was the standard typewriter keyboard designed? Cora: To ask this question, you must be making a mistaken assumption: that typing speed was to be maximized. The real danger with early typewriters was that operators would hit successive keys too quickly, thereby crashing typebars into each other, bending connecting wires, and so on. So the idea was to slow the operator down by making the most common letter sequences awkward to type. Bernard: This is surely not right! These technological limitations have long since vanished, yet the keyboard is still as it was then. Which one of the following, if true, could be used by Cora to counter Bernard's rejection of her explanation? ['Typewriters and word-processing equipment are typically sold to people who have learned to use the standard keyboard and who, ttherefore, demand it in equipment they buy.', 'The standard keyboard allows skilled operators to achieve considerable typing speeds, though it makes acquiring such skills relatively difficult.', 'A person who has learned one keyboard layout can readily learn to use a second one in place of the first, but only with difficulty learn to use a second one alongside the first.', 'It is now possible to construct typewriters and word-processing equipment in which a single keyboard can accommodate two or even more different keyboard layouts, each accessible to the operator at will.']