Investigator: XYZ Coins has misled its clients by promoting some coins

Your doubt is justified but I see D as the most appropriate answer choice indeed.

First of all, for Bold Face CR, method of reasoning and parallel reasoning questions, the range of the words may vary a great deal but still can be considered relevant.

e.g. in "D", although FACTS may be mentioned, but those properties can be considered STRENGTHS as well. Even if that is a part of the law or is a mandate, you can't deny they are strengths at the same time. So, any synonymous words close to FACTS, STRENGTHS, EXTRAORDINARY TRAITS etc. could be considered correct to describe XYZ's rebuttal. The words in these types of question fall in a big spectrum, making the questions more difficult.

The later part of D:
"failing to address the investigator’s charge"

This tells us that the investigator's charge that the coins provided are not rare, but rather commonplace. XYZ doesn't refute this challenge at all. XYZ doesn't say anything such as:
The coins are unique and your theory is baseless and without evidence.
OR
The coins that available outside may look similar but are inherently different from what we provide, so our claim still stands.

"E" could be correct IF investigator said something like this:
XYZ Coins market its coins as "extremely rare" and trying to deceive the customers, for most customers don't actually understand what "extremely rare" actually means.

From the argument, it is clear that both parties agree on the usage of the word "extremely rare", a word neither of them thinks needed clarification.