Based on the context in paragraph 2 of the "Address to the Niagara Movement", the intended meaning of the phrase "assail the ears of" is:
2. harshly criticize
Here is the full paragraph for reference:
"2. We refuse to allow the impression to remain that the Negro-American assents to inferiority, is submissive under oppression and apologetic before insults. Through helplessness we may submit, but the voice of protest of ten million Americans must never cease to assail the ears of their fellows, so long as America is unjust."
The paragraph states that the voice of protest of African Americans must continue to loudly and persistently criticize/condemn the injustices they face. So "assail the ears of" means to harshly criticize or strongly protest against the listeners, in this case their fellow Americans who are allowing the injustices to happen.
The other options do not fit as well:
1. intentionally ignore - does not match the idea of loudly protesting
3. scream loudly at - is too literal, "assail" here is more figurative
4. seek answers from - does not match the context of protesting injustice
Therefore, the best answer is option 2. "Assail the ears of" means to harshly criticize in this context.