The tree diagram is constructed and attached below in the image.
First we have to make a choice out of 3 subjects, so the probability of choosing art as the first subject is 1/3.
Once we have chosen art as the first subject, we have two choices. So the probability of choosing each option now is 1/2. Thus, the probability of choosing math, science is 1/2.
The probability of choosing the projects in order of art, math, science = 1/3 x 1/2 = 1/6
Therefore, the probability that the projects are in order of art, math, science is 1/6 (one over 6). So first option gives the correct answer.
