What happens to words that end in silent "s" when they become plural? an "es" is added to the end of the singular form of the word. an "s" is added to the end of the singular form of the word. an apostrophe and an "s" are added to the end of the singular form of the word. none of these

Personal pronoun, possessive pronoun: object form-singular "s" plural "es" 

Refute it, showing why it is mistaken—an apparent but not real problem; acknowledge its validity or plausibility, but suggest why on balance it's relatively less important or less likely than what you propose, and thus doesn't overturn it; concede its force and complicate your idea accordingly—restate your thesis in a more exact, qualified, or nuanced way that takes account of the objection, or start a new section in which you consider your topic in light of it. this will work if the counterargument concerns only an aspect of your argument; if it undermines your whole case, you need a new thesis.