Using sampling concepts, and considering that skateboarding is a summer sport, the correct option is given by:
a. katie's sample
It is when a group is taken from a population, and the data taken from the group can be taken to estimate the data for the entire population. A sample has to be representative of the population.
In this question, we have to consider that skateboarding is a summer sport, hence June's sample is more representative than January's, which means that option a is correct.
More can be learned about sampling concepts at https://brainly.com/question/25122507