I'd say that 'every' is the adjective you are looking for. It specifies the noun 'light'.
It is not either of the last two options because they would both have the opposite effect on your audience then you would want them to have. So out of the first two choices, I think Using a tone of frustration when describing how difficult it is to eat with forks and spoons would help you relate to the audience the best, making your argument the most compelling. Choice B is what I would go with.
In a group discussion, the best reason that you should respect the opinions of others, even if you do not agree with them is because, it will improve your listening skills and understanding of other points of view. This way, open-mindedness is also improved. At the same time, you will enrich your own ideas more by comparing it to others.
C is the answer. Because deleterious is the opposite of helpful. And ominous is the opposite of friendly.
