I'll freely admit that a lot of these may depend on specific terminology used in your class; it can vary quite a bit from university to university. With that said, here's what appear to be the common sense answers to someone who graduated a year and a half ago with an economics major.
#1: -Make your decision based on the next best alternative use of your time compared to the benefit of one more hour of study
#2: -Gains from trade
#3: -A decrease in quantity and an indeterminate change in price
#4: -its production possibility frontier shifts outward
#5: -final goods and services produced in the economy in a given period
#6: -decreased
#7: -Per capita GDP (in my experience, there's an emphasis on this being Real GDP, aka GDP adjusted for inflation, and not simply nominal GDP, but this may not have been a focus of your class)
#8: -a decrease in aggregate demand
#9: -must be out of work and actively looking for a job
#10: -Shift the aggregate demand curve leftward
#11: -when economic output is less than its potential (I'm not really a fan of any of the answers here. A recession is technically defined as two or more consecutive quarters of negative GDP growth, so...the second answer makes the most sense, but doesn't seem correct. The first and fourth answers are definitely wrong)
#12: -Productivity in many US industries increases because of technological advances
#13: -a decrease in investment spending
#14: -Not as certain here. Technological change would be my instinctive answer, but I'm not confident in this one.
#15: -fixed prices and interest rates. Again, not as certain; I suspect this will be a list specifically designed by your professor or the textbook from the course. Off the top of my head, I do not believe that whether prices and interest rates are fixed should affect long run productivity.
#16: -a rise in government transfers as more people receive unemployment insurance benefits
#17: -the public debt will increase
#18: -reserve requirements, open market operations, and lending directly to banks. I believe. I'm quite confident reserve requirements and open market operations are on there, but the third tool I've heard most consistently is the discount rate, which is the rate at which the central bank (in the US's case, the federal reserve) loans money to other banks. I will admit I have no idea what margin regulations are, so if that means something similar to the discount rate, probably go with that.
#19: -Not certain, I'm not particularly familiar with the workings behind determining expected inflation.
#20: -The dollar has appreciated
