Answer:
Experiment
Step-by-step explanation:
The teacher is researhing the effect of what type of font she uses on a test and the scores on the test to see if there is a relationship, which means the aim of the test is to confirm some certain hypothesis and generate results.
She randomly gives half her classes tests with Times New Roman font and half her classes tests with Comic Sans font and then tracks their test scores for a semester which makes the test be under controlled condition.
Recall that an Experiment is a a test that is conducted under controlled conditions to understand the relationship between two or more variables or to confirm a certain hypothesis.
Therefore, the study above is an example of Experiment.