#6 - The introduction of symbols for numbers is an event

[maximbasu]

Hello,
I chose A as the correct answer while the correct answer was D.

I reasoned that D was a mistaken reversal or at the very least stated one of the premises word for word.

early symbols --> 20K years ago
systematic methods invented --> 5K years ago --> computation


Thank you, Maxim.

[Nikki Siclunov]

Maxim,

The author observes that the earliest known number symbols date back 20,000 years, whereas a systematic method for writing numerals wasn't invented until 5,500 years ago. From this, she concludes that computation only became available 5,500 years ago. Clearly, the author must be assuming that a systematic method for writing numerals is a necessary condition for computation. This prephrase agrees with answer choice (D).

The argument is not about the grooves and scratches, but about the origins of computation. Even if some of the grooves and scratches resulted from natural processes (the logical opposite of answer choice A), that would not affect the validity of the conclusion.

Hope this helps!

Thanks,