It is nearly impossible to discern which number the solver has placed incorrectly once an error is discovered. If you don’t have a pencil, use a pen to write the digit as a series of light dots.

Question

It is nearly impossible to discern which number the solver has placed incorrectly once an error is discovered. If you don’t have a pencil, use a pen to write the digit as a series of light dots.
*
1 point
no change
a number
that number
number

GPT-4o mini · Answer

The best choice to maintain clarity and improve readability in the sentence is "that number."

So, the revised sentence would be:

"It is nearly impossible to discern which number the solver has placed incorrectly once an error is discovered. If you don’t have a pencil, use a pen to write that number as a series of light dots."