Answer: B. And while we perceive there from that the zeal and love of your mind towards us is not diminished, yet in part we are grieved that we cannot gratify your Serene Highness with the same kind of affection.
Step-by-step explanation: From the given sentences, the one that is the best textual evidence to Ethan to use to support his inference that Queen Elizabeth thinks Erik of Sweden is needlessly vain is the corresponding to option B, because here Queen Elizabeth implies that they will never have the same affection for Erik that the one he has for himself, showing that she considered him very vain.