GMAT Question of the week
The numeric working memory of young orangutans are astonishing: flashing a random scattering of numerals on a screen for half a second and then covering the numbers with white squares, a numerically schooled young orangutan will touch the squares sequentially to indicate the ascending order of the numbers hidden beneath.
E) is astonishing: flash a random scattering of numerals on a screen for half a second and then cover the numbers with white squares, and
Anytime you see a clear subject-verb agreement decision point in the answer choices – here the choice between “are” and “is” – start by analyzing that. Using slash-and-burn to get rid of modifiers, you see the core sentence is really: The memory…IS or ARE…astonishing. Clearly, it must be “is” so you can confidently eliminate (A), (B), and (C) because of that subject-verb agreement error with “are.”
The only remaining differences between (D) and (E) are the choices of “flashing…and covering” vs. “flash and cover” and the use of “and” at the end. To see which is correct, read the core elements and consider meaning: for (D) without the “and” at the end, “flashing…and covering…” are then participial phrases modifying orangutans…but that makes no sense! The orangutans are not both setting up the experiment and then indicating the ascending order in the experiment.
Only (E) with the use of the imperative verbs “flash” and “cover” and the word “and” creates a logical meaning for how the experiment works: [you] FLASH the numerals and then COVER the numbers, AND a young orangutan will be able to indicate… The correct answer is (E).