Hello there!
First, let's remind what ethos is.
The use of ethos is called an "ethical appeal." Note that this is very different from our usual understanding of the word "ethical." "Ethos" is used to describe the audience's perception of the rhetor's credibility or authority. The audience asks themselves, "What does this person know about this topic?" and "Why should I trust this person?"
Now, in that sense, correct answer is D: Our languages the reflection of ourselves, and if you tell me that our languages are too poor to express the best thought, then say that the sooner we are wiped out of existence the better for us.
In answer D, he stated: the sooner they are dead, the better. This option uses ethos as a persuasive device as he is using language as a use of ethos (language is a characteristic and it is spiritual.) In addition, he uses death and existence to be persuasive and to get the message out there by using a sensitive and a heart touching topic.
Hope this helps.