a. Agnostic = who's an atheist b. Agnostic = who denies any answer on the questions about God's existence c. Agnostic = who denies that any abstract or metaphysical concept can be found/answered d. Agnostic = who denies any necessity to answer on the question about God's existence
A. There's no need for such an agnostic to exist B. Such an agnostic is nothing, but an active atheist. There's no reason to being him C. Unlike the previous one this one wants to sure us that we cannot find anything metaphysical, and therefore it doesn't need to be studied. Well, this completely contradicts to the modern science, and the common sense as well. Since Aristotle said that those speculations are indeed necessary for us to develop thinking, there's no reason to follow this close-minded path D. Well, such a person could be even a theist. Indeed, if it was a Christian who didn't want to deal with theology, but to follow the Christ's rules, he might think that such answers were unecessary. Also, such a person is diminish many questions, and that's why it's no need to follow this path either.
Thomas Jefferson wrote to his nephew Peter Carr in 1787, advising the young man to "Question with boldness even the existence of a god; because, if there be one, he must more approve the homage of reason, than that of blindfolded fear."
Even if one does not identify as an Agnostic, and professes and practices a specific faith, one should still- at every turn- question that faith and its teachings to determine if they make sense and if one truly believes in those things. I do not have the audacity to claim to know God's mind, but I'm reasonably sure he'd rather have us following him because we truly believe in him and have sound reasons for doing so instead of just going through the motions because 'that's what my family has always done'.