Read the Original Sentence Carefully, Looking for Errors:
It's worth confirming that the underlined pronouns "he" and "his" have a clear antecedent, and they dos: "he" and "his" refer to the noun directly following the introductory phrase, "Pylades." Don't be thrown by all the Greek names in this sentence. The grammatical structure appears to be correct. Keeping in mind (A) as the correct answer, quickly review the remaining choices in case you missed a subtle error in the original.
Scan and Group the Answer Choices:
The answer choices begin with a variety of words ("Except", "Besides", "Excepting" and "With the exception"). There is no way to usefully group the choices, so move on to consider each one.
Eliminate Wrong Answer Choices:
Eliminate (B). It changes the verb "delivers" to "delivered," conflicting with the present tense "remains" in the second part of the sentence.
Eliminate (C). Because it's the "line" and not the "delivery" that causes Pylades to speak, (C) has an incorrect object for "besides."
Eliminate (D) because it changes the meaning of the original sentence. "Excepting ... command" becomes an introductory modifying phrase that must refer to the first noun following it, "Pylades." However, Pylades is not "excepting" his line—he is speaking it.
Eliminate (E). Like (B), it changes the verb "delivers" to "delivered," conflicting with the present tense "remains" in the second part of the sentence. Also "With the exception of" is a long way of saying "Except," and "as a reminder to" is a long way of saying "to remind." Such wordiness is never correct on the GMAT when a more concise and correct answer is available.
Only (A) remains, and it is the correct version of the sentence.
TAKEAWAY: Take a moment to plug your answer back into the original sentence to make sure it makes sense. Doing so can help you avoid picking an answer that is appealing in one respect but introduces an error.