Generally, and you should know this, . You should be able to see this from your previous experience building confidence intervals.
After that useful forumla, B) and C) are eyeball problems. If you increase the numerator or decrease the denominator, what does that do to the required sample size? Similarly, if you decrease the numerator or increase the denominator, what does that do to the required sample size?
Note: It should be obvious that a small sample would lead to 't' rather than 'z'.
Note: With a Finite Population Correction Factor, this will be different. You tell me what that is. We don't need it for this problem. Why?