Oh, and I can't use loop.
What's this about?? AHA!!!--perhaps one of the constraints in your homework assignment?
First, you do not mount directories. Mount refers to attaching a device
to the filesystem so that it can be used to read/write.
Second, Linux cannot be fooled. It will outsmart you every time.
Please give us the real problem......e.g. do you want to know how to mount a CD or DVD?