Using confidence interval concepts, it is found that:
Given a confidence interval with two bounds a and b, the margin of error is half the difference of the two bounds.
So, for an interval that is (8%, 12%), the margin of error is given by:
M = (12 - 8)/2 = 2%.
Which means that for the first question, option B is correct.
Additionally, an increase in the sample size results in a decrease of the margin of error, which means that for the second question, option B is also correct.
More can be learned about confidence interval concepts at https://brainly.com/question/25890103