a) Let X be the number of no-shows. If we assume independence of events, then X has a Binomial distribution with n = 52 and p = 0.04. A flight will be overbooked if X=0 or X=1, and then
I'll let you do the computation.
b) There are many common factors that might influence multiple passengers. For example, if the weather is bad then many people might not make it to the airport on time.
c) Whoever wrote this question believes something like bad weather is likely, so several passengers might not show up. However, it is by no means certain that the actual probability is less than that calculated in part a). Lack of independence can also make it more likely that people will show up, increasing the probability of overbooking. For example, suppose the weather is unusually good for a change. Then you have the reverse effect of bad weather and people are more likely to make it to the airport on time. So lack of independence can increase or decrease the probability of overbooking, and without additional evidence we can't really say which is more likely.