I'd answer "D" just because it is a word-for-word quote straight out of the umpire manual where it describes our positioning for tag plays.
Without the benefit of having memorized the manual verbatim, or having in available for reference, I'd probably waffle between "C" and "D". Are they not essentially saying the same thing? Isn't the "base PATH" the same thing as "the path of the runner"? Isn't "just short of the base, at a depth of 10-12 feet" the same thing as "10-12 feet from the play"?
And then I'd probably curse under my breath the ASA tendency to offer multiple choice answers with seemingly redundant differences, as well as their continued use of the pronoun "they" (a plural construction) to describe a single runner!
BTW- tried to log into the chat last night, but was unsuccessful. Now that I think about it, I bet that it was held 7:00-10:00
eastern time and I was trying to log in just after 9:00
central time and the chat was already over.