Answer:
c)
Step-by-step explanation:
Hello!
The researcher took a random sample of 20 rats.
First left each of them inside a dark maze for 5 minutes and recorded how far each rat got.
Then, using the same random sample, she "illuminated" the maze with UV light and repeated the experiment, recording how far the rats got after 5 min.
At the end of the experiment, the researcher has two distances recorder for each rat, one in the darkness and one illuminated with UV light. Since both variables "distance traveled in the dark maze" and "distance traveled in the maze illuminated with UV light" were measured using the same experimental units they are dependent.
Z-test is more accurate when sample sizes tend to infinite (for example larger than 100) and t-tests are more accurate for small samples. The sample is n=20 so the best statistic is the t-test.
The test to apply is a Paired-samples t-test.
I hope it helps!