What is the hardest libral art course for engineering students?

Liberal Arts are things like Humanities and Geography. It really depends on what the student’s strengths and weaknesses are, but I’d say something in the Literature department. I only guess that because literature is so malleable, and engineers have a tendency to see the world through a set of rules in black and white (not always a bad thing!) so I could see someone of that mind-set struggling.

It depends on the student and their effort. Some subjects are easier for some than others. Some people no matter how good or bad they are at something put in more effort that others. It depends on the person.

The traditonal scope of Liberal Arts includes math & astronomy. I will assume that you are, however, referring to humanities.

Advanced courses in Logic can be challenging (but fun). Also, technical writing is rough for certain students. Although I love to read, especially classics, I found that finding the time to read non-fiction for literature courses to be a real drain on my study time.