Google forms will not allow you to merge several forms which I have found to be a huge issue. I usually take multiple quizzes and combine them for the test. Here is the work around that I have found to be the easiest:
Start with the largest form. Then add your questions. What I do to make the copying and pasting go quicker is I put the other forms in preview mode (make sure your shuffle is turned off) and then I copy and paste from that view. Double-clicking inside the sentence will highlight the whole thing and you can ctrl-C and Ctrl-V from there. Secondly, you can copy the radio buttons and paste in the first answer box on the form and it will automatically create the same number of questions. I also create a template with the number of points filled out and copy those down that way the only thing I have to worry about selecting the correct answer.
Hope this helps!