It's A as to the avoiding double negation which is not possible in English.
Most often, it is deciphered through A) context clues. Some people, however, choose to decipher them through B) pronoun references. Just to be on the safe side, I'd choose A) context clues because most often, the words that are being deciphered are they themselves the pronoun.
The correct answer is A.
In this passage, the writter does not provide evidence to support his claim. Being part of the body of the essay, the writer should concentrate on providing information and examples that would help support the claim he has made earlier on the essay.
