Correct option is A
The correct answer is
(a) By virtue of being readers we are also writers, I now believe, but that was not always the case.
Explanation: Option (a) has no spelling errors. The other options contain errors such as "vertue" (should be "virtue"), "riters" (should be "writers"), and "beleive" (should be "believe").
Correct sentence: "By
virtue of being readers we are also
writers, I now
believe, but that was not always the case."