Can you please help me understand the answers to this vignette in the attached image?

1. What is the independent variable?
2. What is the dependent variable?
3. Were the students randomly assigned to levels of the independent variable here? please explain
4. Please Explain: Whichstatistical techniquewould Dr. Jacobs use to test significance? Select the correct answer and explain why: a. one-way ANOVA; b. dependent t-test; c. two-way ANOVA; d. multiple regression
5. When could a t-test be used (based on this vignette)? please explain

Dr Jacobs is recruiting freshmen at Bayesian College to examine the effect of stress on studying. 60 volunteers participate in his study. The students are informed that this is a study related to the effects of stress on studying. They consent to participate. 20 of the College freshman volunteers are randomly assigned to TX A, 20 to TX B and 20 to TX C. All Participants receive a word list and a 3 page story to read and are asked to remember the contents. The TX A group spends an hour studying in a room, and nothing surprising happens. The TX B group spends an hour studying in a room, but the proctor pretends to collapse and is given aid by a student confederate from the group. The TX C group spends an hour studying in a room, but one (student confederate) draws a gun and threatens the students, then leaves. At the end of the study, the participants are given the Jacobs Stress Scale (JSS), a widely used scale and the researchers compare stress levels for the different treatment groups