Read the passage "This semester, with some trepidation, I decided to take a class on Shakespeare's tragedies. I appreciate that Ms. Robertson establishes clear expectations for students: the course requirements are rigorous but fair. On the first day of class, she handed out a detailed syllabus listing all the required readings, in-class projects, homework assignments, and tests. THe course is definitely challenging, but in a good way, and Ms. Robertson is always very supportive and encouraging." Select two words that are most similar in meaning to "rigorous" as it is used in the passage.
A: Demanding
B: Harsh
C: Rigid
D: Severe
E: Thorough
A: Demanding
E: Thorough